Presentation on theme: "U.S. Department of the Interior U.S. Geological Survey Seismic sensors and networks: Hawaii Earthquake Preparedness Workshop La Serena, Chile December,"— Presentation transcript:
U.S. Department of the Interior U.S. Geological Survey Seismic sensors and networks: Hawaii Earthquake Preparedness Workshop La Serena, Chile December, 2007 Paul Okubo, Geophysicist Hawaiian Volcano Observatory
Hawaii: volcanically and seismically active Active subareal shield volcanoes: (1) Kilauea and (2) Mauna Loa Active fault systems in volcanic edifice and in lithosphere 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-real- time 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)
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 Pu’u O’o fountain episode in 1984 VOLCANO MONITORING
-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) 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.
Hawaii Earthquake History Figure adapted and updated from Wyss and Koyanagi, 1992 Large earthquakes in Hawaii have been recorded throughout its written history, dating back to 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
From: Klein and Kirby, 2007
Hawaii Probabilistic Seismic Hazard Map
-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) 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.
From: Klein and Kirby, 2007 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 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: 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 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.