HR: 14:00h
AN: S33C-01 INVITED     [Abstracts]
TI: Seismic Data Monitoring at U.S. Tsunami Warning Centers
AU: Whitmore, P M
EM: paul.whitmore@noaa.gov
AF: NOAA/NWS/West Coast and Alaska Tsunami Warning Center, 910 South Felton Street, Palmer, AK 99645, United States
AU: * Ferris, J C
EM: justin.ferris@noaa.gov
AF: NOAA/NWS/West Coast and Alaska Tsunami Warning Center, 910 South Felton Street, Palmer, AK 99645, United States
AU: Weinstein, S A
EM: stuart.weinstein@noaa.gov
AF: NOAA/NWS/Pacific Tsunami Warning Center, 91-270 Fort Weaver Road, Ewa Beach, HI 96706, United States
AB: Seismic data are critical to Tsunami Warning Centers (TWCs) as most tsunamis are caused by earthquakes: 1) directly through static sea floor displacement, or 2) indirectly by sub-aqueous landslides triggered by strong shaking. While tsunami size does not have a direct correlation with earthquake magnitude, seismic data typically provides the first indication that a tsunami may have been generated. TWCs require a certain signal reliability and seismometer density throughout their region which are related to response time and mission requirements. For example, in order to consistently issue messages within five minutes of an earthquake's origin time, the following seismometer network criteria must be met: 1) 12 properly-distributed stations, 2) within 900 km of the source region, 3) 80 percent seismometer uptime, 4) maximum 30 seconds data latency, and 5) high-quality digital, broadband seismic data. This seismic network configuration will provide 9 to 10 P-wave arrivals within 150 seconds of the earthquake origin time. Approximately sixty seconds of the P-wave signal is required to measure moment magnitude for large earthquakes. This provides an analyst 30 seconds to review the event and an additional 60 seconds to compose and transmit the appropriate message (a total of five minutes). Increasing seismometer density will lead to decreased response times, though the decrease in response time is limited by source process time, analyst review, and message creation time. Conversely, decreasing seismometer density and uptime, or increasing latency will have a negative effect on response time. There are currently sixteen regional, national, and global seismic networks supplying data to the TWC's virtual seismic network. In total, approximately 250 stations are monitored in real-time and processed to determine the likelihood of tsunamigenesis. TWCs can monitor data latency and seismometer uptime with earthworm modules, and latency times and outages are summarized yearly to monitor network performance.
DE: 4564 Tsunamis and storm surges
DE: 7219 Seismic monitoring and test-ban treaty verification
SC: Seismology [S]
MN: 2007 Joint Assembly