HR: 17:15h
AN: S32E-06    [PDF]
TI: Global Travel Time Tomography Using ANSS Real Time Data
AU: * Villasenor, A
EM: antonio@geo.uu.nl
AF: Faculty of Earth Sciences, University of Utrecht, P.O. Box 80021, Utrecht, 3508 TA Netherlands
AU: Sandoval, S
EM: senen@geo.uu.nl
AF: Faculty of Earth Sciences, University of Utrecht, P.O. Box 80021, Utrecht, 3508 TA Netherlands
AU: Spakman, W
EM: wims@geo.uu.nl
AF: Faculty of Earth Sciences, University of Utrecht, P.O. Box 80021, Utrecht, 3508 TA Netherlands
AU: Benz, H M
EM: benz@usgs.gov
AF: U.S. Geological Survey, Box 25046, MS 966, Denver Federal Center, Denver, CO 80225 United States
AU: Earle, P
EM: pearle@usgs.gov
AF: U.S. Geological Survey, Box 25046, MS 966, Denver Federal Center, Denver, CO 80225 United States
AU: Engdahl, E R
EM: engdahl@colorado.edu
AF: University of Colorado, Campus Box 390, Boulder, CO 80309 United States
AB: As part of the implementation of the Advanced National Seismic System (ANSS) waveform data of a large, growing number of seismic stations from US regional networks is being received in near real time at the National Earthquake Information Center (NEIC) in Golden, CO. A very large number of these stations are only used for regional earthquake monitoring and therefore do not report routinely arrival times from teleseismic events, which could be very useful for imaging in great detail the upper mantle structure beneath the continental US. The availability of this large volume of waveform data in a single data center allows us to carry out the processing (phase picking) in an efficient and consistent manner. For this purpose we have developed a procedure that combines automatic absolute picking, followed by more accurate relative picking using waveform cross-correlation. The algorithm is automated in order to handle the expected large data flow (currently about 40 monitoring networks operate in the US for a total of 3,000 stations) but also allows for interactive quality control. In its testing phase we have processed 125 events occurred in 2002-2003 which provided 18,688 new P-wave arrival times, more than in most teleseismic experiments. We have used these new travel times in combination with a large global dataset of reprocessed ISC data to obtain a global tomographic model of P-wave velocity structure. Although the model is global, the most visible improvements are in the western US, where the data increase and station density is largest. Preliminary results show a more detailed image of the structure in the upper mantle, also due to the incorporation of regional travel times in the new global dataset. A particularly well-imaged feature is the subducted Juan de Fuca slab beneath the Pacific Northwest. The slab is sharply defined between 100 and 410 km depth, extending from the Puget Sound region through Oregon to Northern California, well south of the Mendocino triple junction. We anticipate that with the incorporation of additional networks and the processing of new events the resulting tomographic models will provide significantly improved images of the upper mantle seismic structure beneath the continental US.
DE: 7203 Body wave propagation
DE: 7218 Lithosphere and upper mantle
DE: 7294 Instruments and techniques
SC: Seismology [S]
MN: 2003 Fall Meeting