Distributed, high-performance earthquake deformation
analysis and modelling facilitated by Discovery Net
Jian Guo Liu1, Moustafa Ghanem2, Vasa Curcin2,
Christian Haselwimmer1, Yike Guo2, Gareth Morgan1, Kyran Mish3,
1
Department of Earth Science and Engineering, Imperial College, London
2
Department of Computing, Imperial College, London
3
Fears Structural Engineering Laboratory, University of Oklahoma
Abstract
A Discovery Net project that has been investigating the relationship between macro and micro-scale
earthquake deformational processes has successfully developed and tested a geoinformatics infrastructure
for linking computationally intensive earthquake monitoring and modelling. Measurement of lateral coseismic deformation is carried out with imageodesy algorithms running on servers at the London eScience
Centre. The resultant deformation field is used to initialise geo-mechanical simulations of the earthquake
deformation running on supercomputers based at the University of Oklahoma. The paper describes detail
of this project, initial results of testing the workflow, and follow-on research and development.
1. Introduction
Earthquakes are important geo-hazards that can
produce significant land surface deformation and
ground shaking causing damage to built infrastructure
and loss of life. Understanding the dynamics of
earthquake deformation is therefore important for
earthquake hazard assessment and insight into the
effects of ground shaking on built environment.
Increasingly, grid-enabled, high performance
computing is enabling geoscientists to model
neotectonic and earthquake processes across a range of
spatial and temporal scales (from modelling earthquake
ground shaking to the tectonic evolution of fault
systems). In addition, advances in satellite remote
sensing, such as GPS, InSAR (Inteferometric SAR),
and sub-pixel image feature matching based on local
correlation (imageodesy), are providing precise
geodetic measurements of surface deformation at high
resolution and with a broad synoptic coverage isolating
the key features.
The linkage of remote sensing derived
measurements and physical models is a common
feature of a variety of earth system sciences, such as
meteorology and oceanography. However, until now
the coupling of remote sensing measurement with
computer simulation in order to investigate earthquake
crustal deformation has been limited to simple
analytical modelling [1] that may not effectively
simulate the complexity of the earthquake system. In
this paper we present an overview of the results of an
e-Science applications project entitled “Bridging the
Macro to Micro: a computing intensive earthquake
study” (henceforth abbreviated to M2M). This project
has developed a geoinformatics infrastructure for
investigating earthquake dynamics by linking
computationally intensive, remote-sensing based
measurement of land surface movement with highperformance geo-mechanical simulations that model a
range of physical processes as well as take into account
the spatial variability in material properties in three
dimensions.
2. Background
Earthquake studies that link remote sensing with model
simulation are usually conducted at the macro-scale
and are restricted to investigating regional patterns of
deformation and their cause and effect. However, the
macro phenomena of earthquakes are often composed
of micro-scale displacement features and kinematic
indicators (e.g. shear and extensional fracture patterns)
that show the dynamic nature of the deformation. In
addition, micro- and nano-scale processes along active
faults are fundamental to the segmentation, initiation
and halting of earthquake rupturing and may be
important in accommodating the release of strain
disparate from the main rupture zone. Hence,
understanding and modelling the relationships between
macro and micro-scale deformational phenomena may
lead to a better understanding of the dynamics of
earthquake deformation.
The imageodesy technique, which is based on
sub-pixel local correlation is an example of macro
analysis conducted within earthquake studies. It maps
lateral co-seismic deformation by measuring the
differences in position of corresponding image features
between a pre- and post-earthquake satellite image.
The technique has shown to be effective at mapping
the lateral deformation associated with earthquakes,
particularly in the area near an earthquake rupture [5],
and complements existing geodetic methods for
measuring co-seismic ground movement (e.g. InSAR ,
GPS).
Finite Element Modelling (FEM) is an example
of micro analysis conducted within earthquake studies.
FEM is a well-established technique for determining
stresses and displacements in objects and systems. In
the field of earthquake engineering, FEM is used
extensively by structural and geotechnical engineers to
investigate the effects of earthquakes on infrastructure
such as buildings, bridges, and dams. In addition,
FEM-based simulations are used in the fields of
structural geology, and neo-tectonics to model transient
stress and deformation due to tectonics. Applying FEM
to model remote sensing imageodesy results is a
promising approach to investigate the stress field and
faulting mechanism of macro scale earthquakes
through micro scale computing simulation.
Imageodesy and FEM techniques are both
compute-intensive applications that require access to
specialized software components executing on high
performance computing facilities. The aim of our
work presented here is to enable users to integrate the
use of these techniques within the same earthquake
study.
The work undertaken in this project is built
around the analysis of data from the Ms 8.1 Kunlun
earthquake, which occurred in northern Tibet in Nov
2001. This event was the largest earthquake in China
for 50 years and produced a massive surface rupture
zone of over 450 km making it the longest rupture of
an earthquake on land ever identified. The magnitude
and nature of the earthquake along with the large area
that was affected provide the perfect natural laboratory
in which to investigate earthquake dynamics and test
the novel geoinformatics approach that has been
developed during this research project.
workflows can be published through web portals and
Web/Grid services, allowing users to execute
distributed computations interactively and to analyse
the results of their execution using a variety of
visualisation tools.
As part of the M2M project, the Discovery Net
infrastructure has been extended to enable integration
of the domain specific measurement and modelling
services based at Imperial College and the University
of Oklahoma. Processing routines, developed within
Matlab, have been integrated into this workflow to
enable post-processing of imageodesy output and
preparation of input data for the finite element analysis
software. When packaged together, this workflow
provides:
• Seamless integration between measurement and
modelling services.
• One-click execution with minimal user input
(e.g. to define material parameters).
• The workflow has been packaged as an open
web-service that has the potential to be used by
the earth science community.
3. Implementation
The implementation of the geoinformatics workflow
has been based on the Discovery Net informatics
infrastructure [4]. Discovery Net is a grid-enabled
software analytics platform developed at Imperial
College London, funded through a UK e-Science Pilot
Project and extended within this work. The platform is
based on a service-based computing infrastructure for
high throughput informatics that supports the
integration and analysis of data collected from various
high throughput devices.
Within Discovery Net, end-user applications are
constructed within a visual authoring environment as
workflows that represent the steps required for
executing a particular distributed computation, and the
flow of information between these tasks. Within each
workflow, analysis components are treated as services
or black boxes with known input and output interfaces
described using web service protocols. These services
can execute either on the user’s own machine or make
use of high performance computing resources through
specialised implementations. Also, Discovery Net
Figure 1: Imageodesy refinement workflow
The methodology that has been developed as part
of the M2M project uses regional measurements of coseismic deformation to directly run high-resolution
geo-mechanical simulations of the earthquake
deformation based on the Finite Element Method
(FEM). Macro-scale measurements of surface
deformation are retrieved using sub-pixel FNCC (Fast
Normalised Cross-Correlation) imageodesy algorithms
that have been developed [2] and refined [3] by the
geo-application research team of Discovery Net. These
algorithms measure the lateral co-seismic deformation
(horizontal image feature shift and long a fault line)
associated with an earthquake from pre- and post-event
satellite images. The algorithms are computationally
intensive and are implemented on supercomputers
based at the London eScience Centre. The output
deformation field produced by this software provides
the input into a Finite Element analysis system, which
is running on servers based at the University of
Figure 2: W-E shear strain (left) and N-S shear strain (right) during the Kunlun earthquake predicted from running
finite element analysis on low-resolution imageodesy-derived co-seismic measurements using a simple 2D
homogeneous elastic model. The predicted N-S shear strain field is particularly interesting as it highlights the
predominantly left lateral faulting in the area.
Oklahoma. Discovery Net is used to orchestrate the
domain-specific tasks (Figure 1).
The finite-element segment of the analysis was
implemented on high-performance servers based at the
University of Oklahoma. The TeraScale computational
architecture [8] was used as the basis for construction
of a finite-element application capable of ingesting
macro-scale imageodesy measurements. The TeraScale
framework was employed for this task as it provides
the tools for building feature rich finite-element
applications that are easily interoperable and readily
scaled to the available or required computing
resources. The finite-element application built during
this research project enables automatic mesh creation
and the initialisation of model runs using the kinematic
data as boundary conditions within a full-physics geomechanical simulation that includes the effects of
momentum conservation and material characterisation.
The resultant finite-element model can be used to
estimate residual stress distribution induced (or
relieved) in the seismic region. In addition, macro-tomicro scale analysis is achieved by using the macroscale kinematic measurements to define boundary
conditions for higher resolution finite element models.
In effect, this means that measured displacements
define the boundary conditions at the edges of highresolution finite element meshes.
4. Results
As part of the initial experiment, the Discovery Net
geo-application research team has developed and
applied imageodesy algorithms to cross-event Landsat
7 ETM+ satellite imagery for the Kunlun earthquake
[2].
Due to the large size of the input datasets and
demanding nature of the algorithms, implementation
was carried out on a MPI parallel computer within the
London eScience centre. The results have revealed
stunning
patterns
of
co-seismic
left-lateral
displacement along the Kunlun fault and presented the
first 2-D measurement of regional deformation
associated with this event [6]. In addition, interesting
patterns of deformation south of the main fault have
led to the discovery of previously unreported surface
rupturing south of the main Kunlun fault [7].
We have further refined imageodesy algorithms
developed as part of this pilot project [2] to include
data refinement and post-processing algorithms [3] that
improve the quality of the imageodesy output by
removing systematic noise. The images shown on
Figure 3 show the full width of the central part of the
original scene. In these images, blue to green indicates
shift to the left and yellow to red indicates shift to the
right. The red arrows in the filtering refined image
indicate the Kunlun fault zone along which the massive
earthquake occurred. As the result, the terrain block
south to the fault moved toward east (right). We can
see how the vertical noise is very visible after the
horizontal shift has been removed, while in the result
produced by FFT selective and adaptive filtering; the
horizontal striping and the multiple frequency wavy
patterns of vertical stripes have also been successfully
removed. This clearly revealed the phenomena of
regional co-seismic shift along the Kunlun fault line as
indicated by three arrows.
The workflow and software we have developed
has been successfully tested using low-resolution
imageodesy measurements to run a simple
homogeneous elastic model of the seismic region
(Figure 2). The macro-scale results highlight the
predominantly left-lateral deformation (which ranges
from 1.5-8.1m) during the Kunlun earthquake in the
modelled N-S shear strain field. In addition, this result
indicates the presence of unexpected but significant
shear features in the northwest of the study area that
are currently under further investigation.
5. Conclusions
The applications research conducted in this project has
successfully developed and tested an analytical system
for linking kinematic measurements of earthquake coseismic deformation with geo-mechanical modelling to
enable investigation of the dynamics of earthquake
crustal deformation at macro-to-micro scales. This
approach is both novel in its use of distributed high
have adopted will seek to incrementally increase the
modelling resolution, improve how the models are
parameterised (e.g. with realistic geological properties
for the region), and strive to simulate the full range of
physical processes involved with earthquake
deformation.
Following on from our initial low-resolution, 2D
model runs we intend to run much higher resolution 2D
analyses before ultimately undertaking 3D simulation
of the seismic region. Parameterisation of these models
will be undertaken with a more realistic
characterisation of the material properties of the region.
Due to the flexibility and interoperability of our finite
element application the implementation of these
increasingly
complex
simulations
will
be
straightforward and will allow us to concentrate on
interpreting the results.
References
[1] Okada, Y., 1985, Surface deformation due to shear and
Figure 3: Filtering image noise. The original X-shift image
on top is badly contaminated by stripes revealing the
compensation errors of two way cross-track scanning.
Using novel frequency selective and adaptive FFT filters
this has been effectively removed without subduing the
lateral shift information of co-seismic deformation.
performance computing and its application of advanced
analytical and modelling tools to real-world problems.
With respect to geoinformatics work involved, a
number of discoveries have been made:
• Novel patterns of co-seismic left-lateral
displacement
• First 2D measurement of the Kunlun earthquake
• Novel rupturing south of the main fault
• Unexpected shear northwest of the main area.
One of the most important considerations when
developing a valid geo-mechanical simulation is the
ability to properly characterise the material properties
of the region under investigation. Conventional
approaches to the coupling of remote sensing
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analytical methods that assume homogeneous
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realistic and heterogeneous material representation of
the area under simulation. This ability is of particular
importance when it comes to understanding the
relationship between macro- and micro-scale
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of stress and strain.
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