U.S. Department of the InteriorU.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

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3

Earthquakes M>1.3, located by USGSOct 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 1983.

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 beenrecorded 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

From: Klein and Kirby, 2007

Hawaii Probabilistic Seismic Hazard Map

http://earthquake.usgs.gov/research/hazmaps/products_data/Hawaii/

-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 withcontinuous data collection and exchange

ANSS - Advanced National Seismic SystemOperated 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.