International Forum on Satellite Earth Observation for Geohazard Risk Management.
Perspectives concerning Satellite EO and Geohazard risk
management: the way forward.
Draft community paper concerning seismic hazards.
Date of Issue
Status
18/04/2012
Draft 1.0
Coordinators of the International Forum:
Philippe Bally (ESA).
Francesco Gaetani (GEO Secretariat).
Lead Authors:
Salvatore Stramondo – Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy.
Tim Wright – School of Earth and Environment, University of Leeds, UK.
Contributing Authors:
Barry Parsons, University of Oxford, UK; Gerald Bawden (USGS), USA; Marsh Stuart, BGS (British
Geological Survey), UK; David Norbury (EFG).
Acknowledgements:
This paper received editing input from Philippe Bally (ESA), Francesco Gaetani (GEO Secretariat),
Geraint Cooksley (Altamira Information), Andrew Eddy (Athena Global) and Michael Foumelis
(ESA).
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CONTENTS
1 SCOPE OF THIS COMMUNITY PAPER ................................................................. 4
2 SEISMIC HAZARDS AND GLOBAL EXPOSURE .................................................... 5
3 USERS AND THEIR INFORMATION NEEDS WITH REGARDS TO GEOHAZARD
RISKS....................................................................................................................... 10
4 THE EUROPEAN CASE ........................................................................................ 12
5 THE GLOBAL PERSPECTIVE............................................................................... 15
6 CURRENT STATE OF SATELLITE EO BASED APPLICATIONS & SERVICES........ 17
6.1
6.2
7
THE WAY FORWARD ......................................................................................... 28
7.1
7.2
7.3
8
Main EO capacities used or in development : ....................................................................... 18
Emerging research concerning seismic risk assessment: ..................................................... 27
Technology and services: .................................................................................................... 30
Science ............................................................................................................................... 35
Users and practitioners ....................................................................................................... 37
REFERENCES ..................................................................................................... 38
ANNEX 1 ...................................................................................................................................... 45
APPENDIX 1. ................................................................................................................................ 47
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This document is a draft of a series of papers with the scope of reflecting the community
perspective on geohazards. It forms the basis for discussion to be held at the International Forum
on Satellite Earth Observation for Geohazard Risk Management organised by the European
Space Agency on May 21-23, 2012 (www.int-eo-geo-hazard-forum-esa.org). The authors invite
comments and further contributions from the community on this paper so they can be collated
and discussed at the conference. The document will be updated on the basis of this discussion.
Comments should be addressed to esa.conference.bureau@esa.int with the title of the draft paper.
1
Scope of this community paper
0B
This paper presents the perspectives concerning how Satellite Earth Observation (EO) can
contribute to Geohazard & disaster risk reduction in seismic hazards with a focus on the Geohazard
community looking at seismic risk. Its primary focus is on user organizations with an operational
mandate for seismic risk management and seismic risk management users such as national and
regional civil protection organisations, seismological centers, and a range of other actors including
non-governmental organizations, academic institutions and international organisations. This paper
outlines a 5 to 10-year vision for the seismological community, based on the assessment of state of
the art research and the application of EO in seismology and seismic risk management. This
document builds on the 3rd International Geohazards workshop of the Group of Earth Observation
(GEO), held in November 2007 in Frascati, Italy, which recommended “to stimulate an
international effort to monitor and study selected reference sites by establishing open access to
relevant datasets according to GEO principles to foster the collaboration between all various
partners and end-users”.
This paper aims to achieve a shared view of the community of geoscience users involved with
seismic risk mitigation and using Satellite EO. It aims to define the issues and opportunities
associated with the use of satellite data to support science users and operational users in seismic
risk management in the context of newly available and planned EO missions that will supply very
large volume of observations. This raises issues relating to the capacity of EO missions, the position
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of mission operators and data owners and the acceptance and level of uptake from risk
management authorities concerning the exploitation of EO based geo-information products and
services.
Community papers are being elaborated for other types of geohazards for discussion at the
International Forum on Satellite Earth Observation for Geohazard Risk Management (May 21-23,
2012) in Santorini, Greece. Other EO geohazards addressed include landslides, volcanic eruptions
and land subsidence. The scope and theme of these community papers are described in Appendix 1
2
Seismic hazards and global exposure
1B
Even though there have been significant advances in our understanding of seismic hazards over the
past two decades, society continues to habitat these seismically prone regions. The last decade has
seen significant losses of life and property and devastated economies in the wake of several
devastating earthquakes and the associated tsunamis.
Seismic hazards constitute one of the most visible natural catastrophes in human history and they
can wreak havoc with well-prepared cities and decimate ill-equipped nations. In the past decade,
there have been a number of seismic disasters have marked our collective memory. In December
2003, the city of Bam in Iran, a UNESCO World Heritage Site, was destroyed by a M w 6.6
earthquake, killing around 30,000 people. In December 2004 a 9.3 event struck of the coast of
Indonesia producing a tsunami that resulted in about 300,000 deaths in Indonesia, Thailand and
India. In 2010, Haiti, one of the world’s poorest nations, was struck with a M w 7.0 earthquake,
resulting in more than 225,000 deaths. In stark contrast, when a similar event occurred in March
2011 in Japan, the Mw 9.0 earthquake caused few deaths, largely due to the level of preparedness of
the society and the strict seismic criteria for building and infrastructures. The induced tsunami
however, larger than foreseen due to the massive size of the quake, killed around 20,000 people on
Honshu Island. The linkage between earthquakes and tsunamis add to the complexity of this
seismic hazard and necessary mitigation measures. Beyond the direct human impact caused by
such events, the economic impact can last years or even decades. It is unlikely that Haiti will fully
recover from the 2010 earthquake for many years. Japan’s entire economy, one of the world’s
largest, was plunged into recession by the impact of the tsunami, which severed key transportation
lines for weeks and generated nuclear safety crisis the effects of which are still being felt.
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These mega events are well-documented throughout history and cannot be prevented. However,
their impacts can be mitigated through improved understanding of their underlying causes, and
concerted actions by planners in areas at risk. This understanding can be achieved through
comprehensive monitoring of the world’s major fault zones and other areas at risk.
Figure 1.1: Global seismic hazard map from GSHA (GLOBALSEISMIC HAZARD ASSESSMENT) PROGRAM
(http://www.seismo.ethz.ch/static/GSHAP/global/).
Since 1900 there have been ~130 earthquakes that have killed more than 1000 people (England
and Jackson, Nature Geoscience, 2011). More than 75% of these occurred in continental interiors
away from plate boundaries, killing more than 1.4 Million (England and Jackson, Nature
Geoscience, 2011). The vast majority of these deaths occurred in the zone where the African,
Arabian and Indian plates collide with Eurasia, known as the Alpine-Himalayan belt (Figure 1.2).
Characterising the seismic hazard in this region is challenging because of its sheer scale. The
Alpine-Himalayan belt stretches for 10,000 km from the European Alps to western China, and in
places is over 2,000 km wide. Many earthquakes in this region occur on faults that were not
identified prior to the event or whose hazard had been previously underestimated.
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Typically, seismic hazard is assessed through analysis of the historic and instrumental earthquake
record – areas that have experienced strong shaking in the past are likely to experience it again
(Aki, 1988). Additional constraints come from the mapped locations and measured slip rates of
Alpine-Himalayan belt
Figure 1.2: Distribution of
earthquake fatalities (19002011). Circles show all
earthquakes with more than
10,000 fatalities (data from
USGS); the area of the circle
is proportional to the number
of deaths and the colour to
the earthquake magnitude.
Earthquakes represented by
circles with black rims did
not
occur
on
plate
boundaries. Adapted from
(England et al., What works
and Does not Work in the
Science and Social Science of
Earthquake Vulnerability?
Report of an International
Workshop held in the
Department
of
Earth
Sciences,
University
of
Oxford on 28th and 29th
January, 2011., 2011).
known active faults. These methods break down when earthquakes are infrequent or faults have not
been identified (Ward, Geophysical Journal International, 1998). For example, the Bam earthquake
(M6.5, Iran, 2003), which killed around 30,000 people, occurred on a fault that was not and
probably could not have been identified prior to the earthquake, in a city that had not experienced
strong shaking for at least 2000 years (Jackson et al., Geophysical Journal International, 2006).
Although earthquakes do not appear to have recognisable short-term precursors, all are preceded
by the steady accumulation of seismic strain over decades to millennia. Short-term measures of this
strain accumulation offer an alternative method for assessing seismic hazard that is not biased by
the brevity of the instrumental record (Bird et al., Seismological Research Letters, 2010). Even with
existing measures of strain (Kreemer et al., Geophysical Journal International, 2003), which are
derived from ground-based observations of surface motions that are often sparse, the relationship
between measured strain and earthquake hazard is strong (Figure 1.3). Few earthquakes occur in
regions where the magnitude of strain is lower than 1 x 10-8 yr-1 (or 1 mm/yr over 100 km length
scales).
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Figure 1.3: Number of earthquakes per square
kilometre (M>6 from the ISC catalogue 1964-2010) as
a function of the magnitude of tectonic strain (second
invariant of strain tensor from (Kreemer et al.,
Geophysical Journal International, 2003).
Despite the clear evidence for the potential utility of strain observations in seismic hazard (e.g
Figure 1.2), most seismic hazard assessments are carried out in a probabilistic fashion using data
from historical and instrumental catalogues of seismicity, supplemented with geological data on
active fault location and slip rates where available, e.g. (Reiter, 1990; McGuire, Bulletin of the
Seismological Society of America, 1995). An analysis by (Ward, Geophysical Journal International,
1998) demonstrated that the long inter-event time of many earthquakes means seismicity
catalogues are inevitably incomplete, especially in areas of low strains. Additional problems arise if
faults have not been identified. For example, the Bam earthquake (M6.5, Iran, 2003), which killed
around 30,000 people, occurred on a fault that could not have been identified prior to the
earthquake, in a city that had not experienced strong shaking for at least 2000 years (Jackson et al.,
Geophysical Journal International, 2006).
Recently, (Bird et al., Seismological Research Letters, 2010) proposed a formal method for utilising
geodetic strain data to provide a long-term forecast of shallow seismicity. They used the Global
Strain Rate Model (GSRM) of (Kreemer et al., Geophysical Journal International, 2003) and some
simple assumptions about the style of earthquakes occurring in each region to forecast shallow
seismicity rates (Figure 1.4). For continental regions, they found good agreement between the
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observed seismicity rates for the past 30 years and those predicted by the model, without any
requirement for adjustment factors.
Figure 1.4: Long-term forecast by (Bird et al., Seismological
Research Letters, 2010) of shallow seismicity (M ≥ 5.66) based
on the Global Strain Rate Model of (Kreemer et al., Geophysical
Journal International, 2003). Colours are earthquake rate in
units of log10 (EQ/m2/s). i.e. 100x100 km regions coloured green
should expect one earthquake per century. This illustrates the
potential utility of measures of strain, but higher-resolution
geodetic data are required to make further progress.
However, the GSRM is constrained in the continents primarily by ground-based GPS data. In many
countries with hazardous faults, GPS data are sparse if they exist at all. As such, any forecast based
primarily on the GSRM can only hope to capture a broad overview of the potential seismic hazard
of a region. Dense geodetic observations are required before further progress can be made. There
also are recent works (Xavier Le Pichon and Corné Kreemer, 2010) assessing the suitability of GPS
for strain rate modeling.
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3
Users and their information needs with regards to geohazard risks
2B
National and Regional Civil Protections, Seismological centers, National and Local authorities in
charge of seismic risk management activities are concerned with the phases of prevention,
preparedness, early warning, response, recovery, rehabilitation and reconstruction. Beyond
operational users with a mandate in seismic risk management there is a range of geoscience users
focused on the scientific use of data with the main goal of understanding the physics the drive
earthquakes thereby improving our ability to characterize, understand, and model seismic risk.
There are essentially four main user communities involved in seismic hazard activity:
1) Emergency Response – this community is concerned with operational response to major
seismic events, and needs data and information products geared towards damage analysis
and situational awareness.
2) Hazard Science Response – this group uses applied science, advanced imagery analysis and
models during events to help develop the situational awareness needed to help facilitate the
Emergency Response Community, bringing the science into an operational context.
3) Operation Science – this group is concerned with the mechanisms triggering events.
4) Hazard Science Research – this group is focused on pure science research.
The transboundary nature of earthquakes makes satellite EO a pertinent source of data and
imagery to assist both the science and operational communities. Both science users and operational
users have an interest in satellite EO, with different but complementary objectives and
requirements, as outlined below.
The science users of seismic risk management require satellite EO to support mitigation activities
designed to reduce risk. They are carried out before the earthquake occurs, and are presently the
only effective way to reduce the impact of earthquakes on the society –short term earthquake
prediction today offers little promise of concrete results. The assessment of seismic hazard requires
gathering geo-information for several aspects: the parameterization of the seismic sources,
knowledge of historical and instrumental rates of seismicity, the measurement of present
deformation rates, the partitioning of strain among different faults, palaeoseismological data from
faults, and the improvement of tectonic models in seismogenic areas. Earth Science users are
interested in exploiting the full range of capabilities that satellite data can offer. These include the
mapping of surface features associated with faulting using high-resolution imagery and elevation
data, and the measurement of surface deformation using interferometric SAR (InSAR).
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Many faults appear to enter a quasi-steady-state phase of the deformation cycle following the
earthquake and after the rapid post-seismic transient surface deformation have decayed; this is
referred to as inter-seismic deformation period - between the earthquakes. Here, the rates are
slower than post-seismic deformation rates, so to make reliable measurements, scientists require
large numbers of acquisitions over extended periods of time to reduce the impact of atmospheric
noise and subtle changes to the land surface know as incoherency in the imagery. Furthermore,
errors in the satellite orbits can introduce artifacts and noise that are distributed across the imagery
at scales matching the inter-seismic deformation with length scales of 100 km or more, thereby
masking or mimicking the tectonic signal that is sought. Given that most seismic belts that have
significant hazard have strain rates higher than 10-8 yr-1 (1 mm/yr over 100 km, measuring the
horizontal and vertical surface velocity gradients to this level of accuracy needs to be a science
requirement for future InSAR missions.
Operational users of seismic risk management do have needs for geo-information to support
mitigation, although the need for situational awareness during response often receives more
attention. Satellite EO can contribute by providing geo-information concerning crustal block
boundaries to better map active faults, maps of strain to assess how rapidly faults are deforming,
and geo-information concerning soil vulnerability to help estimate how the soil is behaving in
reaction to seismic phenomena. On an emergency basis, the first information needed after a large
earthquake occurs is an assessment of the extent and intensity of the earthquake impact on manmade structures, immediately after which it becomes important to formulate assumptions on the
evolution of the seismic sequence, i.e. where local aftershocks or future main shocks (on nearby
faults) are most likely to occur. For both of these, rapid acquisition of InSAR data can provide
critical information, showing the extent of faulting and deformation, and allowing simple models to
be built. A very important piece of information in seismic crisis management is the so-called “event
scenario”, whose goal is to provide the authorities in charge with key elements to address, such as
for instance, the choice of emergency housing locations, evacuation strategies, or specific safety
measurements for manmade structures. In an event scenario an assessment of the short-term
spatial evolution of the seismic sequence may be attempted, even if likely affected by large
uncertainties, due to the knowledge gaps still existing in earthquake dynamics.
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4
The European case
3B
In Europe most of the seismic regions are concentrated in the areas around the Mediterranean Sea.
A moderate to strong seismicity is present in Italy, Greece, Morocco, Algeria, the Balkan peninsula,
up to Turkey to the East. The North Anatolian Fault System (NAFS) that cuts Turkey from East to
West along 1,200 km is, along with the San Andreas Fault in California (USA), the longest strike
slip fault system worldwide. The NAFS is characterized by a frequent seismicity with two main
events occurring in 1999, the August 17 magnitude 7.6 Izmit earthquake followed on November 12 th
by the magnitude 7.2 Düzce earthquake to the east and thousands of aftershocks. Additionally
southern Spain and Portugal (Lisbon earthquake) cannot be forgotten. From a seismological
perspective all the main types of faulting are present in Europe. Besides the normal faulting in Italy,
Greece, major strike slip structures are in Turkey, finally the Hellenic arc is a well-known example
of thrust faulting.
In order to have a clear idea about the geographic priorities of the seismic risk management
community in Europe the map in Figure 2 can be considered. Taking into account those nations
where one or more seismic areas are known it appears that most of the Mediterranean regions can
be listed. Based on the surface extent of seismically prone areas at Global scale, the “European
problem” is about 11% of the extent of seismic areas in the world.
Fig.2: Extent of seismic prone areas in Europe, derived from Figure 1.1.
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The Istanbul metropolitan area is, amongst large metropolitan areas, one of the cities most prone to
seismic risk worldwide. Istanbul's long history of earthquake damage relates to the NAFS that
passes only a few tens of kilometres away beneath the Sea of Marmara. During the last 500 years at
least eight earthquakes with magnitudes greater than 7, have occurred close to Istanbul - causing
high casualties and great damage. A complete picture of recent events and historical is provided by
figure 3, below. Recent studies show that the probability of an earthquake greater than 7 affecting
Istanbul within the next 30 years now stands at 53%. Rapid population growth (10-fold in the last
50 years) has resulted in hastily constructed new building stock that often does not comply with
required standards. About 65% of the total building stock does not satisfy current codes.
Figure 3: Estimated sources of the historical earthquakes based on the macroseismic data and seismicity of
the region in 20th century (Ambraseys and Finkel, 1991)
In recent years, Athens in 1999 and the Ionian islands (Lefkada, Cephalonia, Zakynthos) in 2003
experienced moderate and damaging earthquakes. The recent seismicity in Italy is characterized by
the 1980 Irpinia earthquake (M 6.9) that devastated large areas in Campania region and caused
thousands of fatalities. In 1997, Umbria-Marche regions were hit by a moderate earthquake (M 6.0)
whose epicentre was near the historical city of Assisi. Finally, in 2009 L’Aquila city in Abruzzo
region (Central Italy) was devastated by a M 6.3 earthquake. More than 300 fatalities and
thousands of houses heavily damaged where the effects of the main shock.
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Large efforts have been made in the coordination of the research infrastructures at European scale.
A Collaborative Project in the Cooperation programme of the Seventh Framework Program of the
European Commission, SHARE started in 2009 to provide a community-based seismic hazard
model for the Euro-Mediterranean region with update mechanisms. The project aims to establish
new standards in Probabilistic Seismic Hazard Assessment (PSHA) practice by a close cooperation
of leading European geologists, seismologists and engineers.
SHARE is one of the Regional Programmes of the Global Earthquake Model or GEM
(http://www.globalquakemodel.org/) providing essential input and feedback on all hazard
assessment procedures and standards in Europe. SHARE and GEM are working together in the
development of a computational infrastructure for open-source probabilistic seismic hazard
assessment. Further activities are ongoing concerning the management of earthquake crises.
Among them are REAKT (Strategies and tools for Real time EArthquake risK reduction looking at
real time seismic risk reduction methodologies stemming from probability models), NERA
(Network of European Research Infrastructures for Earthquake Risk Assessment and Mitigation),
VERCE (Virtual Earthquake and seismology Research Community in Europe e-science
environment), EUDAT (EUropean DATa).
Since 2002 ESFRI (European Strategy Forum on Research Infrastructure) has been leading the
strategic plan and further initiatives have been derived from it at National and European scale. It is
the case of the Italian Roadmap of the Pan-European Research Infrastructures of Interest that is
the basis of the National Research Strategy for Research 2011-2013. Moreover it led to the start of
the strategic project EPOS (European Plate Observing System) coordinated from Italy through the
Istituto Nazionale di Geofisica e Vulcanologia (INGV). EPOS is aimed at coordinating Research
Infrastructure and e-science for Data and Observatories on Earthquakes, Volcanoes, Surface
Dynamics and Tectonics. Originally, the EPOS project was limited to using in situ data. More
recently, the need to augment these data with valuable satellite EO has been recognized. The
working group WG8 ‘Satellite Information Data’ is the link between the EO data community,
composed of the EO data providers and EO product providers, and the in situ data community.
Taking into account the requirements of the different user communities, Terrafirma provides
PSInSAR maps to EPOS by sharing its database of surface velocity maps. Later on Terrafirma will
add PSInSAR maps to the EPOS Core Services to allow the full integration with other data (GNSS,
leveling, etc).
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5
The global perspective
4B
Considerable effort has been put into the global aspects of seismic hazards over the past decade,
ranging from the setting of strategies for mitigation and observation to the sharing of
experiences from different continents. Following the International Strategy and then Decade for
Disaster Reduction in the 1990s and early 2000s, the strategic aspect was picked up first by
CEOS and then brought into sharper focus when they joined with the UN agencies and the
science programmes under the International Council for Science to form the IGOS Partnership.
This was dedicated to the setting of International Global Observing Strategies, one of which was
developed for geohazards that had earthquakes as one of its four main themes.
The IGOS Geohazards Theme Report, published by ESA in 2004, sets out a long-term (10-years
plus) strategy for the better observation and monitoring of earthquakes. One of the main
strands was to build a stronger global geohazard community and this has been taken forward
for earthquakes by increased cooperation over that decade amongst the global seismic
community, principally through the development of the Global Seismic Network, GSN.
Terrafirma and ESA could once again become more involved in this process of community
building, having contributed strongly to the earlier work.
The IGOS Partnership was an excellent forum for designing strategy but it lacked political
stakeholders and so implementation was on a best-endeavours basis amongst the partners. This
is one of the main reasons for the formal establishment in 2005 of the Group on Earth
Observations (GEO), an intergovernmental organisation with the sole objective of building the
Global Observing System of Systems (GEOSS). Once GEO was established, with almost 100
Member States, and the IGOS Partners had joined it as Participating Organisations, the IGOS
Themes were then integrated into its 10 year Work Plan during 2009. Thus GEO has been
responsible for implementing the strategy through its Disasters Societal Benefit Area (SBA).
This has a series of Tasks or Sub-Tasks focused on different elements of the disaster response
cycle. Most are not specifically focused on earthquakes but rather on multiple hazards.
However, one of the main relevant Tasks relates to the expansion and upgrading of the GSN,
who are also now a Participating Organisation.
The establishment of a number of global Supersites (as described in section 6.1), natural
laboratories for the study of geohazard processes and the improvement of the observing system,
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has focused strongly on major fault zones. Several of the existing sites relate to seismic hazards
and in the European context a North Antalya Fault Zone Supersite is likely to be established by
the EC’s framework programme in 2012.
Within GEO, the community building process has continued through the establishment of its
Geohazards Community of Practice (GHCP). This has set out a Roadmap for the Disasters SBA
based on the four recognised stages of the disaster response cycle; preparedness, early warning,
response and recovery. This helped to shape the new GEO Work Plan for 2012-15 and Tasks in
that plan are now taking forward the implementation of the Roadmap. This Roadmap and Work
Plan provide a potential framework for defining new activities on seismic hazards. There are
also activities related to the ESA and EC initiative described in the previous section on Global
Monitoring for Environment and Security that could fit within this framework, including those
in the GMES emergency response core service and within the Global Earthquake Model, which
funds several, relevant observation and modelling projects.
The Community was recently brought together again by the GHCP with assistance from the
European Science Foundation and the COST Office for a High-Level Conference on Extreme
Geohazards and there will be follow-up meetings during the EGU in April 2012. The scientific
focus of these events will then be complemented by the more applied focus of the International
Forum on Satellite Earth Observation for Geohazard Risk Management in May 2012 at the
Santorini Convention Centre in Greece.
The combination of excellent science, a strong observing system, applied projects approaching
their sustainable, operational phase and major industrial players will be critical to plan a more
consolidated approach to dealing with seismic hazards globally.
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6
Current state of Satellite EO based applications & services
5B
EO data and imagery significantly contribute to the emergency response, to prevention &
mitigation and help better understand seismic hazards. This is true in countries with different
levels of risk management and different hazard monitoring methods. In developed countries, dense
seismic networks integrate continuously-operating GPS stations and other in situ data to provide a
complete understanding of seismic hazards. Here, EO data complements the ground-based data by
adding a synoptic view of the surface effects all over the effected region, focusing on deformation
and damage to infrastructure, imaging inter-seismic strain accumulation in regions with limited
seismic network coverage or unexpected seismic hazards, and fully mapping the pre/post-seismic
geodetic displacement field. Developing countries, on the other hand, do not normally have such
sensor networks in place, so that the information available is less detailed, increasing the potential
contribution of satellite EO.
Precise terrain deformations using interferometric (InSAR) data has made a valuable contribution
to the measurement and understanding of all phases of the earthquake cycle: co-seismic, postseismic and inter-seismic. Before InSAR, the horizontal and vertical geodetic displacements
associated with only a handful of earthquakes had been measured using traditional surveying
techniques, such as leveling, triangulation, trilateration, and at the time, very limited GPS. Reliable
fault models can be determined using INSAR data alone and in areas with little to no prior geodetic
networks. InSAR imagery can be used to model and solve for key parameters that are sought to
characterize the earthquake, including the geometry of the causative fault (length, depth, dip) and
the depth and spatially varied slip distribution along the fault rupture.
Thanks to available and planned EO missions Solid Earth scientist has the technological means to
generate a wealth of spatially and temporally dense observations to constrain better earthquake
models and improve the understanding of the fundamental physical processes driving the
earthquake cycle. What is really needed is to make these observations systematic and constant over
a long period of time. Measurement instruments placed on satellite platforms are among the best
ways to provide fast and systematic observation of the Earth surface over large areas and over long
time intervals.
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6.1
Main EO capacities used or in development :
8B
Satellite based data have achieved a central role in the Earth Sciences. Indeed EO images are now
widely used to provide a support to the mitigation of natural disasters and to their crisis
management. This is particularly true in case of earthquakes and for the analysis of the seismic risk.
Specific examples include:

The use of high-resolution optical and topographic data sets for investigating tectonic
geomorphology, paleoseismology etc. Particularly important for forensic investigations of
previous major earthquakes in countries like Iran (e.g. .Walker, Jackson and Baker, 2003)

High resolution optical/radar image matching for deformation

SAR Interferometry
Today seismology represents the field where EO data, and in particular SAR Interferometry
(InSAR),has been most often used. Since the early ’90 the capabilities of InSAR technique have
been exploited to study the surface displacement due to moderate-to-strong earthquakes
(Massonnet et al. 1993; Peltzer and Rosen, 1995; Stramondo et al. 1999; Wright et al., 2001;
Reilinger et al., 2000, 1999; Hector Mine, 2000; Denali, 2002 (Biggs et al., 2007 and 2009); Bam,
2003 (Talebian et al., 2004; Stramondo et al., 2005); Sichuan, 2008 (Li et al., 2008; Chini et al.,
2010), Darfield, 2010 (Stramondo et al., 2011)) up to megaearthquakes, Tohoku oki, Japan, 2011,
(Feng et al., 2012).
Since 2001 the main interest of researchers moved to the investigation of the temporal evolution of
surface deformation phenomena. At the same time, a remarkable improvement of InSAR has been
the development of an innovative approach based on the use of a large dataset of SAR images over
the same area.
The Advanced InSAR (A-InSAR) technique overcomes the limitations of standard InSAR, the
deformation modelling derives more accurate measurement of deformations through the better
estimation of topography and atmospheric phases. Various research groups developed InSAR
multitemporal approaches (Berardino et al., 2002; Crosetto et al., 2005; Ferretti et al. 2000;
Hooper et al. 2004; Mora et al. 2003; Usai, 2003; Werner et al. 2003). The A-InSAR techniques
have already demonstrated their effectiveness in the analysis of slow movements due to active
tectonics. These techniques are useful tools to investigate the earthquakes cycle, the co-seismic and
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post-seismic, and inter-seismic phases. Indeed, recent studies have addressed the detection and
measurement of the aseismic creeping or the inter-seismic movements.
The transfer of scientific results into operational services requires addressing issues such as
standardization of procedures for the SAR data analysis (e.g. InSAR analysis) and uncertainty
determination, development of standard modelling procedures and a thorough assessment of
significance and uncertainty of model results.
The policy of space agencies such as ESA and CSA to maintain repeat image acquisitions over many
seismically active areas worldwide (via the so-called “background mission”) has allowed the wide
diffusion of EO data in seismology. The enormous amount of data in archive (15+ years considering
C Band SAR) illustrates the potential of SAR missions for the monitoring of the strain accumulation
along active fault zones now that new InSAR analysis techniques have been developed and made
progressively more available.
A recent development has been to combine InSAR and GPS to solve for velocities over large
regions. The GPS data provide control on the long-wavelength deformation, and InSAR enables
velocities to be determined on a dense mesh. In western Tibet, for example, Wang and Wright
(2012, in press) combined InSAR data from 5 descending and 1 ascending track to map surface
velocities over ~200,000 km2. They were able to identify significant straining areas away from the
major mapped faults. Other examples are for Greece where the Terrafirma project, DLR, are
combing the analysis of 9 frames with GPS.
Another method that InSAR data are used in seismic hazard assessment is to identify and
characterize the negative effects that subsurface fluid pumping (groundwater, hydrocarbon,
geothermal, and carbon sequestration) and sediment compaction have on tectonic GPS networks.
For instance, Bawden et. al., 2001 (Nature) found that groundwater pumping across the Los
Angeles Basin in southern California (USA) produced horizontal and vertical surface deformation
that is an order of magnitude larger than the expect slip at depth on many of the blind thrust fault
that threaten the region. In many areas, fluid pumping either masked or mimicked the tectonic
signal which makes it difficult to fully resolve the true tectonic signal. InSAR imagery was used to
identify the areas with the greatest vertical and horizontal deformation gradients associated with
fluid pumping, and make site-specific corrections to improve the quality of the GPS time-series and
resulting hazard models. InSAR was also used to isolate the effects of a major hydrologic event in a
southern California that produced several centimeters of localized uplift and horizontal motion that
could have been mistaken for an aseismic slip event on a nearby fault (King et. al, 2007).
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Conversely, InSAR imagery can used to optimize GPS networks by first characterizing the spatial
distribution of non-tectonic surface displacement and then developing the network that either
avoid the managed fluid pumping regions or installs new GPS sites away from regions with the
highest horizontal strain rate gradients identified with InSAR imagery. The development of North
America’s largest tectonic GPS network – EarthScope’s Plate Boundary Observatory. ERS1 and
ERS-2 radar InSAR imagery were heavily used to optimize the networks design along the San
Andrea fault. Furthermore, the InSAR analysis imagery has identified numerous previously
unrecognized faults in regions with managed aquifers (Amelung, et al., 1999; Galloway et al., 1999;
Bawden et al., 2001; Catchings, et al., 2008); faults can be groundwater barriers with differential
water levels across a narrow region, therefore concentrating surface deformation above the faults.
Further geophysical analysis of several of these groundwater barriers has resulted in elevated the
seismic risk for the region.
The EO based offering to the tectonic community comprises a range of different components
ranging from dataset, including very large datastacks, tools to process them (e.g. InSAR packages)
and end-to-end terrain deformation services such as PSInSAR motion measurements.
To support scientific investigations concerning earthquakes the GEO Geohazard Supersites, and
Natural Laboratories (SNL) provide access to space-borne and in-situ geophysical data of selected
sites prone to earthquake, volcano or other geohazards. Although not including end- to- end terrain
deformation services the Supersites are providing access to InSAR data for a predefined list of sites
to support the study of geologically active phenomena. It is a partnership of organizations and
scientists involved in the monitoring and assessment of hazards. Further to SAR data the Supersites
provide GNSS based crustal deformation measurements. The data are provided in the spirit of GEO
-(fully endorsed by ESA, NASA and the National Science Foundation, NSF)- that easy access to
Earth science data will promote their use and advance scientific research, ultimately leading to
reduced loss of life from natural hazards. The aim of the Supersites initiative is to enrich the
knowledge about geohazards by empowering the global scientific community through collaboration
of space and in-situ data providers and cross-domain sharing of data and knowledge. Policy makers
and national agencies will benefit from the new scientific knowledge for the assessment and
mitigation of geological risks. Stakeholders are Agencies responsible for the in-situ monitoring of
earthquake and volcanic areas providing the insitu data, space Agencies and satellite operators
providing the satellite data and, finally, the global geohazard scientific community.
The long term vision for the Supersites is to build on synergies among observing systems (groundbased and space-based) towards a global approach on geohazard with a major focus on improving
the coordination between space and in-situ data providers (see figure 4 below). This effort is
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focused on pre-selected sites and regions (natural laboratories for geohazards) for which an einfrastructure virtually connects data suppliers and users and gives open access to relevant data
sets (archive and fresh). This is applying the GEO data sharing principles to seismic data, GNSS
data and SAR datastacks for InSAR.
Fig. 4: coverage of the sites addressed by the GeoHazard SuperSites and Natural Laboratories initiative.
Presently there are 4 seismic risk sites and 3 volcanic hazard sites along with 4 event Supersites
(http://supersites.earthobservations.org).
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While data and processing are of interest to science users, operational users require information
rather than imagery. The development of information services for risk management users has been
addressed through the development of National and International initiatives.
In parallel, since the Sixth Framework Program (FP6), European projects dealing with the
management of seismic risk, and based on the user requirements, have been funded. Such projects
have provided prototype services exploiting the new satellite technologies and processing
techniques obtained from research.
This is the case of PREVIEW – Prevention Information and Early Warning. Following this
precursor project the European Commission has focused part of the FP7 Program on the
development of pre-operational services based on satellite data (SAFER - Services and Applications
for Emergency Response).
Starting in 2003 in the framework of the GMES Services Element programme of ESA to initiate an
operational services capacity, the Terrafirma represents an 11 million Euro activity to deliver EO
products to operational users to support geohazard risk assessment. After five years of realization
primarily focusing on subsidence and landslides, Terrafirma has started a component looking at
tectonic hazards in Stage 3 i.e. in 2009 with two main services offered to users in Italy, Greece and
Turkey: the crustal block boundary service and the tectonics soil vulnerability service. The activity
has been extended up to early 2013.
Finally the operational Emergency Management Service (EMS) of GMES will start with the new
program GIO (GMES Initial Operations) – a continuation of the SAFER precursor with non-R&D
financing sources with a portfolio of services concerning risk management and natural hazards with
earthquakes as one component. However it is anticipated that the GMES EMS will primarily focus
on emergency-response and limited resources will be devoted to risk assessment and mitigation.
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The tectonic services of Terrafirma cover a portion of the most seismic areas in Europe. In
particular the case studies are Istanbul Metropolitan area and the NAFS (North Anatolia Fault
System) in Turkey, the Messina Strait (Italy), the Ionian Islands and the Corinth-Thessaly-Athens
region in Greece (see figure 6).
Overall looking at the European territories exposed to seismic risk the extent of EO based tectonic
services used to date represent roughly 35-40%.
Fig.6: Surface coverage of EO based tectonic services used to date over Europe and its surroundings. This
comprises the mapping activities conducted at national level and the pre-operational/operational service
deliveries of European projects. The blue semi-transparent mask is an indication of risk prone areas based on
mortality risk zones and total economic losses risk zones derived from a collaborative study performed by the
Columbia University and the World Bank, entitled Natural Disaster Hotspots: A Global Risk Analysis.
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Concerning the operational services of Terrafirma the objective of the Tectonic Theme is to provide
services concerning seismic hazard, oriented by the end user perspective and taking into account
the transboundary nature of tectonics and the extent of the areas generally affected. There are two
categories of services:
- Crustal block boundaries are divided into the following three services:
i) Major and local fault investigation that concerns the analysis of surface movements recorded
at large scale by full resolution PSI products combined with in-situ data (GPS measurements,
optical levelling, geological mapping, seismological scenarios); this allows monitoring along
and across major faults to measure fault slip rates and estimate locking depths; to detect local
active faults reactivated soon after major seismic events and eventually further surface effects
triggered by major earthquakes.
ii) Earthquake cycle investigation that is based on measurement of the surface deformation
along the overall earthquake cycle, mostly pre- and post- seismic phases and using a
comprehensive analysis of the earthquake cycle to better define the hazard in seismic areas. The
post seismic phase can be monitored to measure the amount and the surface extension of
possible deformation rebound or residual strain release. Pre-seismic, or aseismic, deformation
remains an open issue in particular for its modelling complexities; the service is aimed at
providing dense geodetic data to investigate possible signals of the different phases of
earthquake cycle and to understand them.
iii) Vertical deformation sources in urban areas: exploits the PSI analysis applied to measuring
vertical surface movements in urban areas to support investigations of the cause of subsidence
and to identify the source (tectonic vs. non-tectonic/man made) of such effects. This is using the
PSI based motion data, the geological background, the seismicity and the geodetic measures.
-
Soil vulnerability map: the capability of PSI in obtaining very dense spatial data and detailed
measurement of surface displacements provides input data to be added and integrated into insitu measurements to compute soil vulnerability maps and help discriminate between primary
tectonic displacements and secondary, seismically induced, movements.
To support the development of InSAR based risk assessment and to augment the base of
seismology experts using terrain deformation data using space-borne SAR, there is a need to
increase the processing capacity and reduce the computational cost of current processing chains.
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The Wide Area Product (WAP) is a new processing chain foreseen to be a standard for the
upcoming Sentinel-1 mission. This technique allows for the continuous mapping of wide areas with
Persistent Scatterer Interferometry (PSI) providing accurate motion measurements over extended
areas – typically 10 times larger than the conventional processing chains used in SAFER and
Terrafirma. A technical note to investigate the implications of using the TOPS mode of wide swath
Sentinel-1 radar data with WAP interferometric processing has been prepared by DLR. The
applicability of the WAP to exploit Sentinel-1 data may allow aligning the provision of terrain
deformation maps to the huge throughput of the sensor. From the viewpoint of tectonic analysis,
the WAP approach is consistent with the investigation of local deformations and regional
movements originating from active tectonics.
The observational requirements for InSAR applications for seismic hazards can be summarized as
follows:
(A) SAR data:
-
High Resolution INSAR: (i) for hazard inventory purposes (e.g. historical hazard mapping):
continuous observations of descending and ascending mode repeat coverage (maximum
images per year, C and L-band in stripmap mode), the focus is to extend and guarantee
observations over the of the priority seismic belts; (ii) for hazard monitoring purposes:
descending and ascending repeat coverage of hotspots (e.g. most critical faults) with more
than 3 images per month C or L-band.
-
Very High Resolution INSAR: (i) for hazard inventory purposes such as global strain
mapping the smaller swath width and cost limits VHR utility; (ii) for hazard monitoring
purposes on hotspots (e.g. most critical faults): descending and ascending repeat coverage
(e.g. TerraSAR-X every 11 days, CosmoSkyMed every 8 days).
(B) HR Optical/VHR Optical:
(i) to provide background reference imagery: archive image (no more than 1-year old),
panchromatic or true colour composite. (ii) VHR optical for disaster response mapping and
for surface fracture mapping , this data should be better than 5m resolution panchromatic
or multispectral and delivered in near-real-time.
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Detailed comments concerning observational requirements associated with INSAR:
In the case of Sentinel-1 data: provide bi-weekly acquisitions in ascending mode and in descending
mode (i.e. every pass); it is assumed this will be guaranteed over Europe; if this is not guaranteed
world-wide then provide descending bi-weekly acquisitions i.e. every pass plus ascending every
other pass. Both ascending and descending SAR data are required to uniquely resolve the threedimensional (3D) nature of slip on the fault. Some faults are invisible if we only have descending
(or only have ascending) data as their motion is perpendicular to the line of sight. InSAR
measurements of surface displacements only on either descending or ascending tracks alone leave
an ambiguity in determining the motions occurring on the earthquake faults at depth. This issue
can be addressed to some extent with left and right looking satellites such as COSMO-Skymed.
Furthermore, faults act as groundwater barriers, thus, the integration of both ascending and
descending InSAR imagery helps to delineate the genesis of the surface deformation. Inversions of
models using InSAR carried out with both ascending and descending interferograms help remove
this ambiguity in the models. The constraint as far as earthquakes themselves are concerned is
more simple. One needs an archive of ascending and descending data that is updated with enough
frequency to mitigate any loss of coherence, and the flexibility to plan either ascending or
descending acquisitions at short notice after an earthquake. The measurement of strain
accumulation across faults is potentially more important as this can inform the assessment of
seismic hazard globally. Ideally one would acquire every pass on both ascending and descending
tracks over fault zones. Given the short repeat cycle of Sentinel, one could perhaps relax this
constraint to every other cycle.
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6.2
Emerging research concerning seismic risk assessment:
9B
There is a number of emerging research issues which will have a positive impact on the use of
satellite EO for seismic research. Some work is taking place now on the combination of InSAR and
GNSS for large scale velocity fields. Other data fusion work deals with VHR SAR and VHR Optical
data fusion for change image analysis, and the fusion of high-resolution DEMs with optical data for
tectonic geomorphology. In parallel, it is necessary to continue automation of processing,
particularly for Sentinel-1 which will generate very large volumes of imagery. New studies of
interseismic strain accumulation using InSAR have provided effective results. The outcomes can be
used together with GNSS to define global strain rate models and to provide a contribution to the
estimation of seismic hazard.
Earthquake cycle modelling capabilities today integrate EO
measurements too. However further developments are needed for the interseismic phase.
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7
The way forward
6B
There are four fundamental questions that concern the use of Satellite EO to support the seismic
hazard risk management community:

what objectives does this community need to achieve over the next 5 to 10 years?

what factors can accelerate the realization of these objectives? (looking at technology &
services and looking at science)

is the international community ready to collectively address the challenges associated
with these objectives? (role of mandated organisations, role of international
organisations, role of industry? are new partnerships needed?).

what about other users not using Satellite EO? (globally, many users are not aware or
able or cannot afford space technologies)
A vision of an operational seismic risk program in 5 years’ time could aim at providing satellite
observations for continuous surface deformation measurements of the seismic belts - typically 15%
of the land surface - and with the following elements:
1. The creation of a new global strain rate model at high spatial resolution that would
incorporate InSAR and GPS based measurement. This would include the provision of
satellite interferometric data for continuous observations of the seismic belts worldwide.
This model would improve with time as new data are acquired by Sentinel-1A/B, but
accuracies should be sufficient for a first release after 3-5 years of regular acquisitions. The
primary model would show the average deformation rates during the observation period;
areas showing significant deviations from steady-state deformation could also be identified.
2. The creation of a new seismic hazard map based on (1). The results again would be timeinvariant, but would have the advantage of not being reliant on incomplete historical or
instrumental records of seismicity.
3. The rapid response to any earthquakes using a combination of EO techniques and scientific
methods. These would include:
a. Automatic rapid creation and web-publication of co-seismic products derived
interferograms (wrapped and unwrapped) from all available sensors. In addition, for
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non-specialist end users, derived products such as phase gradient maps, combined
with critical infrastructure data, could be produced. Simple identification of fault
breaks could be combined with information about earthquake mechanism to derive
estimated surface offsets.
b.
(Semi-)automatic fault modelling – rapid production and web-publication of fault
parameters using simple techniques. This would gradually build up an archive of
fault solutions analogous to the global CMT catalogue in seismology.
c. Rapid calculation of Coulomb Stress changes on neighbouring faults to assess likely
locations of aftershocks or triggered earthquakes. The fault model in (b) would be
used initially, along with any data on historical seismicity (e.g. from the USGS
archives)
d. Prediction of damage location based on fault model.
e. Rapid estimation of earthquake damage using high resolution optical and radar
imagery, and InSAR coherence.
4. A long-term response to earthquakes element that involves acquiring radar data for years to
decades after an earthquake in order to measure post-seismic deformation. This is
important for understanding earthquake physics.
It is to be noted that the seismic hazard community does not think of a seismic risk monitoring
program in the same way as a volcanic risk monitoring program. There are no reliable precursors
for earthquakes and so one should not expect a short term EO solution to predict them despite the
fact that many studies are investigating the possible signals that might be related to an earthquake.
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Factors that can accelerate the realization of these objectives can be grouped in three categories:
technology and services, science, users.
7.1
Technology and services:
10B
After earthquakes, stresses in the crust and mantle relax through a variety of mechanisms. These
include on-going aftershocks, typically an order of magnitude smaller than the main shock, poroelastic deformation, aseismic afterslip, and visco-elastic relaxation. InSAR has again dramatically
increased the number and quality of these observations, but more is required. The tectonic signals
are typically small, and rapidly decay immediately following the earthquake. To maximize the
chances of observing and understanding these phenomena, rapid revisit times (a few days rather
than a few weeks) are required to ensure high coherence, maximize temporal coverage, and to
enable atmospheric artefacts to be removed.
To measure Earth surface deformation for tectonics an ideal mission would be able to measure
surface velocity gradients of 1mm/yr over 100 km length scales (strain rates of 10 -8 yr-1in multiple
dimensions (east-west, north-south and vertical). Coherent interferograms would always be
possible. To meet these criteria would require:
1.
1. Rapid revisit times (6-12 days): to increase number of observations (to reduce
noise), maximise coherence, and to ensure that data are available quickly after an event. A
constellation of satellites to minimize the revisiting time would be needed.
2. A satellite that is always on when over tectonic areas: to maximise the number of
observations, increase coherence. In other words a dedicated observation strategy in order to
populate a large database of images over the main areas of interest.
3. A high to very high resolution sensor to obtain spatially dense measurements.
4. A satellite that allows measurements of motion in at least three disparate directions: to
obtain three dimensions of surface displacement observations (note that most polar orbiting
systems including Sentinel-1 can only obtain 2D deformation from ascending and descending
combinations; methods for obtaining displacements in the azimuth direction exist, but are
currently significantly less accurate than interferometric measurements of range change).
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5. L-band. The coherence at L-band (~20cm wavelength) is dramatically better than at Cband thus helping simplify phase unwrapping. Ionospheric noise is worse, but that can be dealt
with if there is sufficient band width for split-band processing.
6. Data available in near-real time and free of charge: to maximize chances of early response
to events.
7. Wide swaths: to capture long-wavelength inter/post-seismic deformation and co-seismic
deformation from large earthquakes.
Since the 1990s two Earth Observation missions of the European Space Agency (ESA) have
provided fundamental SAR data for these applications. The ERS and ENVISAT missions were
extremely successful in promoting new Earth science applications of SAR. Based on these data new
analysis techniques have been developed, tested, and standardized for use by service providers on
the market.
Future developments of InSAR are linked to forthcoming missions. At present, besides the
constellations in X band, 4 COSMO-SkyMed satellites staggered in a 16 day orbit and 2
TerraSAR/Tandem X (simultaneous), new C, X, and L band satellites (Sentinel -1 A and B, the
Canadian Radarsat Constellation RCM, Kompsat5, Cosmo2, Palsar2, SAOCOM, etc.) should be
commissioned before 2014 - 2015.
Sentinel-1 and the Radarsat Constellation Mission (RCM) will ensure the continuity of SAR C-band
missions, building upon ESA’s and Canada’s heritage with SAR systems onboard ERS-1, ERS-2,
Envisat, and Radarsat-1 and -2. The first satellite (Sentinel-1A) is due to be launched in mid 2013,
followed by a second satellite (Sentinel-1B) two to three years later. RCM’s intial launch is currently
scheduled for 2014. The Sentinel-1 mission and its data will give the possibility of monitoring
ground displacements (e.g. for earthquake and volcano studies) in the order of a few mm, by the
implementation of InSAR techniques. Sentinel-1A will have a 12-day revisit time, which will
improve to a 6-day effective repeat cycle after the launch of the twin satellite Sentinel-1B, allowing a
weekly monitoring of deformation phenomena over the major seismic areas of the world at
intermediate latitudes. The effective revisit time in some high latitude areas will be as short as 1
day. RCM offers three satellites on a twelve-day cycle, with an effective revisit of 4 days.
Up to now, based on current SAR missions, despite a considerable effort by some mission owners
and operators, not all seismically active area of the world have been systematically covered,
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whereas others, for technical constraints, did not attain a sufficient number of images for effective
deformation analysis. Moreover in many locations only a single acquisition geometry was well
covered, while deformation is best estimated using both ascending and descending geometries. The
higher temporal frequency of observation compared to C-band sensors available today, as well as
the planned regularity of the acquisitions over the areas of interest will allow a more accurate
quantification of deformation rates for both classical InSAR and multitemporal techniques.
The higher monitoring frequency of rapidly evolving deformation sources (as in the early
postseismic phase) will be useful to develop improved models of stress transfer across faults, with
evident benefits on operational applications. The more rapid sampling and improved
interferometric coherence of Sentinel-1 data should also increase the possibility of multitemporal
analysis in areas with less stable surfaces and more changeable environmental conditions. An
important innovation will be the wide swath of Sentinel – 1, i.e. 250 km for the Interferometric
Mode.
The Sentinel-1 mission will continue and improve the data flow provided by previous ESA SAR
missions and to provide the framework for the development of operational services and
applications Scientific applications for EO radar imagery require frequent data acquisitions to
ensure high coherence and minimize post-seismic contributions, and cover a large spatial area at
moderate resolution (let’s say 100 m pixel size).
The impact of the wide swath is significant for tectonic applications, which often occur on length
scales of hundreds of kilometres.. In the usual strip map (swaths 30-100 km wide), low order
polynomials that fit the interferometric phases are typically removed, as they depend on orbital
errors and atmosphere. The wide swath of the IW mode will improve the capability to observe slow
deformation phenomena, such as inter-seismic strain accumulation or post-seismic relaxation, over
large areas, allowing a better separatation of deformation signals from orbital fringes.
Based on the systematic monitoring capacity of Sentinel-1, services for the monitoring of the
seismic cycle can be defined to service public agencies, government agencies, and the industry
sector. In fact it is expected that the analysis of Sentinel-1 data will become part of the routine
activities carried out by national and international agencies involved in seismic and geodetic
monitoring activities to help risk assessment and support civil protection actions and in earthquake
research.
For mapping long-wavelength tectonic strain, measurements over lengths of ~100 km are required.
At this length scale, the atmospheric noise is on the order of 25 mm (Emardson et al, 2003). If no
corrections can be made, then 5 years of Sentinel-1 data (acquired every 12 days) would be
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sufficient to reduce the noise to the level of 1 mm/yr (1 mm/yr over 100 km is equivalent to a strain
rate of 10-8 yr-1) [Wright et al, In Prep 2012]. If 50% of the atmospheric noise can be corrected
systematically using numerical weather models, for example, then only 3 years of Sentinel-1 data
would be required.
The larger swath will help to isolate areas of no deformation in the images, allowing a better
separation among different signals (tectonic, orbital, ionospheric); the larger area will facilitate also
the integration with Continuous GPS measurements of ground deformation.
The constant acquisitions will make possible the creation of the necessary archives for reliable
mapping of co-seismic displacement fields and the generation of detailed models of the seismic
source, within only a few days of an earthquake. Maps of the heavily damaged urban districts and of
locally triggered gravitational deformations will also be generated. All these value-added
information products could be updated at each new acquisition, and released in incremental
versions, to the civil protection agencies.
In terms of technologies, a number of methods are being developed that aim to self-consistent
regional deformation products from InSAR. For example, the Wide Area Product (WAP), being
developed by DLR can combine PS data from adjacent frames to give a PSI map at regional scale.
The velocity field method of Wright and Wang [GRL 2012] allows deformation rates from multiple
tracks, viewing geometries and even satellites to be combined with GPS to form regional velocity
fields that are consistent with all the observations.
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Figure 7: Wide Area Map of Greece provides insight on ground motion hot spots; the German Space Agency
(DLR) processed nine ERS frames using an advanced wide area semi-automated processor to produce a PSI
ground motion map covering a 65,000 Km2 area of Greece. The map shows strong subsidence in the Thessaly
plain as well as ground motion associated with an earthquake in the area close to the city of Athens. This
WAP product over Greece is based on stripmap ERS data however the WAP technique is designed to operate
using data from the upcoming Sentinel-1 mission which will be operated in TOPS mode.
Credits: Based on ESA data - Terrafirma project, background image © TerraMetrics 2012.
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7.2
Science
1B
One factor that could help realize the objective of a new global strain rate model at high spatial
resolution is the development of Geohazard Supersites with Seismic Natural Laboratories where
the whole in situ instrumentations (multisource networks: GPS and Seismic and Corner reflectors
and Geochemistry), the whole EO SAR and Optical data, the multidisciplinary datasets can be made
available. This would used by scientists investigate the preparatory phase of an earthquake.
The multidata-multidisciplinary approach is the only capable to combine and analyse the different
data with the objective of increasing our knowledge of earthquakes. They should stem from
initiatives like the Supersites Initiative for EO data and the in situ laboratories (Corinth, Parkfield
and Alto Tiberina fault).
7.2.1 Method development. Methods that need further work include:

Time Series Processing methods - to ensure that they can work for large areas

Phase unwrapping - this is a major headache for existing processing and many PS and
conventional InSAR results contain unwrapping errors

Orbital errors - refining orbital knowledge using force modelling and GPS tracking should
eliminate orbital errors

Atmospheric modelling - The atmosphere is the biggest source of noise. We won't ever be
able to model the very fine scale turbulence that we often see in interferograms, but weather
models have the potential for explaining long wavelength and topographically correlated
signals in InSAR. These methods need further work.

Mapping large scale velocity fields. Several methods exist for combining InSAR and GPS.
These need further development - in principle, we should be able to combine all the Sentinel
data with GPS to form a deformation map for the entire Alpine-Himalayan belt, for
example. The development and deployment of a network of artificial Corner Reflectors
would be useful, in particular if CRs are installed nearby the GPS benchmarks.
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7.2.2 Modelling. The data have really outstripped the model development when it comes to the
earthquake loading cycle. We don't have a good, self-consistent model that can explain co-seismic,
post-seismic, and inter-seismic deformation (at least not one that is accepted by the community).
We are probably in fact many years from this. Therefore we are in a very different position to the
weather/climate community who can assimilate their observations into a well-accepted physical
model. Lots of work is required on the modelling of geodetic data..
7.2.3 Combination with other EO and ground-based data. EO is only going to be one component of
seismic hazard. We need further work on complementary techniques including palaeoseismology,
seismicity, historical studies of earthquakes, field investigations of active faults etc.
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7.3
Users and practitioners
12B

Gap: User acceptance is the main issue to be improved. Indeed the effective use of EO data
is conditioned by the availability of reference measures on site to allow cross comparison
and for validation purposes. Moreover the results need to be unambiguous and affected by a
moderate and clearly defined error, in order to work with reliable data. The user
requirements are also concerning the costs for EO data processing. This is a practical issue
that often hampers the regular use and the diffusion of such data. Finally, end users are
often not experts on EO data.

Accelerate user federation with vertical actions linking different elements of the value chain
such as science users, operational value adders combining EO and geological and seismic
data, end users exploiting results at decision making level and in the field that look at
downstream areas such as building construction robustness, territorial planning, etc

Accelerate user federation with horizontal actions linking different topics in a multihazard
approach such as combining the different specialist areas of seismology.

Capacity building to develop use of EO solutions by national and local users in countries not
currently exploiting EO based geo-information.
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8
References
7B
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ANNEX 1
13B
Other Satellite EO applications to support seismic risk management
(emergency response):
In developing countries and in remote regions where reference data are lacking the contribution of
space-based sensors covers a broader range of phases of the seismic risk management cycle from
the mitigation and preparedness phases, where EO can help provide asset and exposure mapping,
to the immediate emergency-response and recovery phases where rapid access to space-borne
Optical imagery can support rapid mapping and damage assessment. The Warning and Crisis phase
of seismic risk management concerns activities needed to promptly and effectively respond to the
effects of an earthquake, usually with a priority on the effects on life and infrastructures.
As far as support to emergency response is concerned, much research has been done on earthquake
damage assessment using remote sensing data, and the all-weather imaging capability of SAR data
certainly is a valuable asset to complement HR/VHR Optical imagery (Dell’Acqua et al., 2011).
Today an earthquake damage map obtained from remote sensing data can be provided by ground
surveys in a time frame between 2 and 10 days, depending on earthquake magnitude and
environmental context. In fact, damage areas of moderate magnitude earthquakes (Mw 5.8–6.4)
occurring in developed countries, could be effectively surveyed by ground teams or aerial means in
a couple of days, while for undeveloped regions and earthquakes with Mw > 7 (damage areas of
several hundreds of km2) several days may be needed to obtain a synoptic damage map. The best
sources are HR and VHR Optical data from sensor with a capacity to provide rapid access to fresh
acquisitions. Recent seismic events have also illustrated the capabilities of VHR Optical satellites to
support crisis mapping and damage assessment even if airborne data are generally more precise
with centimetric spatial resolution. Satellite EO sensors do not require authorization to fly and are
more affordable.
A large number of panchromatic and multispectral sensors are available today as illustrated in
various national and international initiatives exploiting imagery to provide rapid information that
can be widely used in post-seismic damage detection.
As far as space-borne SAR is concerned there are several challenges, the first one being the 35-day
revisit interval of missions such as ERS or ENVISAT, too large to match these requirements. A
better operational configuration is offered by very high resolution SAR imagery, and a constellation
of satellites capable of flexible and improved revisit intervals. COSMO-Skymed and TerraSAR-X
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bring a constellation approach which will reduce or eliminate this problem. This will be further
improved with the advent of Sentinel-1 and the Radarsat Constellation Mission. The potential of
both TerraSAR-X and COSMO-SkyMed VHR SAR data for early damage assessment has been
proved during the 2009 L'Aquila earthquake where a large number of images have been acquired
and used to support civil protection authorities soon after the seismic event. Expanding this to the
full disaster cycle, background missions aimed at building up radar archives in tectonic areas will
enable comprehensive understanding of most tectonic deformation. There is a link between
response and mitigation/preparedeness and satellite data used for crisis mapping or damage
assessment can be used to make a useful reference database to further investigate hazards and
risks.
Globally the main mechanism to exploit space technology concerning the response phase is the
International Charter Space and Major Disaster, an international collaboration between Space
Agencies to provide a unified system to access imagery for disaster response. With 14 members
today the International Charter is able to provide rapid access to data from a virtual constellation of
a series of satellites, Optical and SAR, tasked in rush mode to help disaster management centers in
relief actions in the response phase. This activity is focused on hazards with rapid on-set scenarios,
on the hazard impact, and aims to service operational users not science users; the Charter capacity
does not include the generation of interferometric dataset for precise terrain deformation
monitoring. In some instances, the main source of information on the initial impact of an
earthquake is satellite imagery such as data made available through the International Charter Space
and Major Disasters.
EO data provided by the International Charter was invaluable for the
emergency response and situational awareness during the 2010 Haiti earthquake because there was
little seismic infrastructure before the earthquake.
Conversely, the vast spatial extent of the
devastation for the 2011 Japan earthquake and tsunami made it difficult for the emergency
responders to fully grasp the magnitude of the devastation; imagery from the Charter was needed
to provide change detection products for the remote village along the northern coast of Honshu to
characterize and see what remained of the villages and to help guide the emergency response
efforts.
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APPENDIX 1.
14B
Scope of the community papers prepared for the May 2012 International
Forum on Satellite Earth Observation for Geohazard Risk Management
Different Geohazard risk communities represented at the Forum are working on community papers
with the scope to describe the state-of-the-art concerning research & applications and define a 5 to
10 year vision on the use of data from new and planned Satellite EO missions. The types of
Geohazard addressed cover primarily Solid Earth & natural Geohazards and the following themes
are identified:
I) Seismic hazards
II) Coastal lowland subsidence & flood defence
III) Landslides
IV) Volcanoes
V) Other hydro-geological risks (such as groundwater management & inactive mines)
Focus is on the different phases of risk management, in particular hazard identification,
quantification and monitoring for prevention and preparedness.
The contribution of Satellite EO is considered primarily concerning hazard mapping and risk
assessment. Other publications concerning Satellite EO for exposure or asset mapping are available
such as for instance the report ‘Using high resolution satellite data for the identification of urban
natural disaster risk’ (Uwe Deichmann, Daniele Ehrlich & al.) prepared in association with EC/JRC
and published by the Global Facility for Disaster Reduction and Recovery (GFDRR).
Draft community papers will be distributed before the event, will be discussed at the Forum and
will be available for on line for download and open review after the event (www.int-eo-geo-hazardforum-esa.org) with the aim of publishing final papers to be released by the conference
co-organizers. This will be used to produce a scientific and technical publication.
Following the International Forum on Satellite Earth Observation for Geohazard Risk
Management, a scientific and technical report will be released as a joint ESA-GEO publication.
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