Seismic sensors and networks: Hawaii
Earthquake Preparedness Workshop
La Serena, Chile
December, 2007
Paul Okubo, Geophysicist
Hawaiian Volcano Observatory
U.S. Department of the Interior
U.S. Geological Survey
Hawaii: volcanically and
seismically active
Active subareal shield volcanoes:
(1) Kilauea and
(2) Mauna Loa
3
Active fault systems in volcanic
edifice and in lithosphere
2
1
In October 2006, M6.7
lithospheric earthquake (3) and
aftershock sequence, caused
widespread damage, including
some to Mauna Kea telescope
facilities
Though not a problem in 2006,
additional concern regarding
locally-generated tsunamis
associated with crustal
earthquakes
Earthquakes M>1.3, located by USGS
Oct 2006 – Nov 2007
A number of instrument types operated by a number of groups
HVO’s short period stations
•Real time telemetry/near-realtime analysis
•Microearthquake detection
and location on volcanoes
•Narrow band and limited
dynamic range, typically clip on
large events
•Relatively inexpensive: many
stations to monitor a large
area.
-HVO short period vertical
component
-HVO short period multicomponent
-HVO broadband multicomponent
-HVO accelerometer
-HVO future broadband
-Borehole sites
-NSMP digital strong motion sites
-PTWC
-IRIS (1 big island, 1 Oahu)
VOLCANO MONITORING
Pu’u O’o fountain episode in 1984
By tracking microearthquake hypocenters occurring in swarms on the active volcanoes,
it is possible to infer the location of the active dike. For example, the apparent
downrift migration of epicenters shown above allowed volcanologists to deploy in time
to see the start of Kilauea’s east rift zone eruption in 1983.
USGS (HVO and NSMP)
broadband and accelerometer
stations
-Improved data quality
-Record a wider range of
frequencies.
-Stay on-scale during large
earthquakes.
-Mix of real-time and polled
systems
-Require greater telemetry
bandwidth/power, generally more
costly.
-HVO short period vertical
component
-HVO short period multicomponent
-HVO broadband multicomponent
-HVO accelerometer
-HVO future broadband
-Borehole sites
-NSMP digital strong motion sites
-PTWC
-IRIS (1 big island, 1 Oahu)
Hawaii Earthquake History
Large earthquakes in Hawaii have been
recorded throughout its written history,
dating back to 1823.
The 19th century seems appears to have
been more seismically active than the 20th
Century, but,
With the connection of seismicity to active
volcanism. There is no reason to think that
Hawaii will not have future large - and
potentially devastating earthquakes.
Church damaged by October 2006 earthquakes
Figure adapted and updated from Wyss and Koyanagi, 1992
From: Klein and Kirby, 2007
Hawaii Probabilistic Seismic Hazard Map
http://earthquake.usgs.gov/research/hazmaps/products_data/Hawaii/
Stations operated by other
agencies, data shared with HVO.
Data imports and exports via
dedicated links and internet.
Expand and improve monitoring
scope beyond the active
volcanoes.
HVO data shared in return,
principally to Pacific Tsunami
Warning Center on island of
Oahu.
-HVO short period vertical
component
-HVO short period multicomponent
-HVO broadband multicomponent
-HVO accelerometer
-HVO future broadband
-Borehole sites
-NSMP digital strong motion sites
-PTWC
-IRIS (1 big island, 1 Oahu)
Large Earthquakes and
Tsunamis
Earthquakes in
1868,1908,1951, and 1975
produced tsunamis;
Special concern for
tsunamigenic event occurring
on western coast of island exposure to Honolulu and
other islands
From: Klein and Kirby, 2007
Home along SE coast, washed off its foundation
and 25 m inland by 1975 tsunami
Seismic monitoring in Hawaii - recent incentives
• December 2004 Sumatran earthquake and
Indian Ocean tsunami
tsunami monitoring upgrades for NOAA and
USGS GSN - teleseismic and local
major goals: report local earthquake location and
magnitude within 90s of event origin time and issue
tsunami bulletin within 5 minutes
• October 2006 Island of Hawaii earthquakes
USGS operational upgrades
major goals: improved earthquake reporting
products generation and delivery
Coordinated seismic monitoring in Hawaii - goals
Monitoring activities cover earthquakes, volcanoes,
tsunamis, and landslides
Operate a reliable and robust statewide system to
record earthquake ground motions over the relevant
range of frequencies and shaking levels
Distribute clear, reliable information about
earthquakes and their effects rapidly after their
occurrence for emergency response and public
information
Create an easily accessible archive of Hawaii
earthquake data and information - including
waveform data and derived products - for
engineering and scientific applications and research
Establish modern, State-wide seismic monitoring capabilities with
continuous data collection and exchange
ANSS - Advanced National Seismic System
Operated and managed by the USGS;
Groups seismic monitoring activities in
the United States into seven (7) ANSS
US Regions:
Northeast US;
Central and Eastern US;
Intermountain West;
California;
Pacific Northwest;
Alaska;
Hawaii ;
and Puerto Rico and US Trust
Territories.
The USGS and its supported
networks are responsible for
earthquake reporting in the US
(based on NEHRP legislation
and “Stafford Act”).
Earthquake early warning
Operational early warning systems exist in Japan, Mexico,
Romania, Taiwan and Turkey.
In the US - spearheaded in California by the California
Integrated Seismic Network partners, including the USGS early warning systems are being developed and tested.
Systems can be characterized as network-based or onsite
warning systems.
Earthquake early warning in Hawaii for Mauna Kea telescopes?
Simple considerations from actual earthquakes:
1. 1975 Kalapana M7.2 earthquake on SE coast of Hawaii Island
P-wave propagation time to closest seismic station = 2.05s
P-wave propagation time to Mauna Kea (Hale Pohaku) = 11.40s
S-wave propagation time to Mauna Kea approx. 20 s
2. 2006 Kiholo Bay M6.7 earthquake off NW coast of Hawaii Island
P-wave propagation time to closest station = 6.77s
P-wave propagation time to Mauna Kea = 9.22s
S-wave propagation time to Mauna Kea approx. 16 s
Earthquake early warning in Hawaii for Mauna Kea telescopes?
Very preliminary thoughts:
Time frame for first registration of earthquake signals can be reduced
by increasing seismographic network density, essentially put stations
closer to possible earthquake locations.
There might be approximately 20 s between first recognition of a
large earthquake and the onset of strong shaking at Mauna Kea, longer
intervals for earthquakes occurring in more distant Hawaii source regions.
Draw from experiences of early warning systems and efforts in other parts of the
World, and, depending on assets and resources, implement or adapt for Hawaii.
Use historical record and seismic hazards modeling to help with design and
construction.