This PowerPoint helps students to consider the concept of infinity.
Seismic sensors & networks paul okubo
1. 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
2. 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
In October 2006, M6.7
lithospheric earthquake (3) and
2 1 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
3. A number of instrument types operated by a number of groups
4. 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)
5. 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.
6. 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)
7. 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
10. 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)
11. 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
12. 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
13. 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
15. 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”).
16. 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.
17. 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
18. 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.
Notas del editor
Earthquakes located by the USGS Hawaiian Volcano Observatory. Symbols are color-coded according to depth, sized to reflect magnitude. There are 5240 earthquakes on this map.
Seismic monitoring groups in Hawaii: US Geological Survey Hawaiian Volcano Observatory, National Strong Motion Project, and Global Seismographic Network; National Oceanic and Atmospheric Administration Pacific Tsunami Warning Center
Hawaiian Volcano Observatory (HVO): emphasis on volcano monitoring and using microearthquake information to infer magma location and transport Automatically detect and locate earthquakes, hypocenters available within minutes. Data analysts interactively review to produce final catalogs.
Graph shows hypocenters projected onto plane parallel to Kilauea east rift zone, and plotted as a function of time between December 26, 1982 to January 9, 1983. Seismicity migrated clearly downrift, and HVO volcanologists actually saw the start of the eruption on January 3, positioning themselves on the basis of the earthquake locations.
USGS has operated accelerometers since 1973 to record large earthquakes in Hawaii for data that assists engineers. Historically, these recorded on film (SMA-1), but now these use digital technologies and can be telemetered. Operated along with broadband seismometers, greatly improved data are available and can be used in enhanced data analysis and data product generation. The earthquakes are simply recorded better.
Hawaii has a long record of large earthquakes. The written records extend to 1823. Instrumental recording began in 1912, so the graphs are separated at that point. Each line on the graph indicates the time of a M6 or larger earthquake. (Derrick Salmon willtalk about October 2006 earthquake a little bit.)
Large historical Hawaiian earthquakes: black dots are crustal, depths to 15 km which is basically within or at the base of the volcanic edifice. Gray dots are “lithospheric” earthuqakes deeper than 15 km. More earthquakes beneath the active volcanoes.
Can describe future earthquake behaviors in terms of seismic hazards maps. HVO seismicity catalog, available USGS strong motion data are key elements that go into the seismic hazard modeling.
The Pacific Tsunami Warning Center is concerned with tsunamis generated both teleseismically and locally. To help PTWC monitor large local earthquakes, HVO exports realtime seismic waveform data to PTWC.
Tsunami wave transit times from locally generated earthquakes is very short. Rapid earthquake processing and notification is very important. Tsunami travel time from west coast of Hawaii to Honolulu is approximately 20 minutes.
In addition to October 2006 Hawaii earthquakes, 2004 Sumatran earthquake and Indian Ocean tsunami brought increased focus on seismic monitoring in Hawaii. The result is an opportunity to upgrade and modernize.
It will be important to achieve the upgrades effectively and without unnecessary duplication of effort. USGS and NOAA have agreed to the principle of coordinated seismic network operations while adhering to Bureau-specific requirements and missions. We have begun to develop and implement the idea of a Hawaii Integrated Seismic Network to accomplich these goals.
The HISN will extend across the entire State of Hawaii to provide authoritative reporting capability on earthquakes occurring in the region.
The HISN will operate as a part of the USGS Advanced National Seismic System project. The ANSS is built on partnerships among the USGS andother seismic monitoring interests across the US. Performance of the HISN, as well as the ANSS in general, is tied to the ability to generate and disseminate reliable earthquake information products developed and supported by the ANSS. USGS support to do this is available, but individual networks also retain the ability to develop their own capabilities, especially if other funding sources impose different Requirements or provide alternatives.
Based on data. Earliest recognition of earthquake = P-wave first arrival at closest station. Strong shaking/potential for damage? Use the arrival of the S-waves.
