Collaborative Research: Calibration for IMS Stations in Eastern Asia
COLUMBIA UNIV PALISADES NY LAMONT-DOHERTY EARTH OBSERVATORY
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We have competed a three-year consortium effort led by Lamont to improve the capability to locate seismic events based on data acquired by 30 International Monitoring System IMS stations in East Asia We have developed and tested Source Specific Station Corrections SSSCs for Pn and Sn travel times at these 30 IMS stations or suitable surrogates, and for 127 other stations used for validation testing. First we developed SSSCs via a 3-D model of the P-wave velocity for East Asia, and then we refined them empirically by applying a kriging algorithm to travel-time residuals for 525 Ground-Truth GT events whose epicenters in East Asia we showed are known to within 5 km. Using a leave-one-out approach, we relocated these 525 events recorded by various combinations of 140 regional stations. Miclocations were reduced for 66 of the events using the model-based SSSCs and for 85 of the events using kringed SSSCs. Meridian miclocation improved from 16.9 km to 11.4 km and 6.5 km respectively. Median error ellipse area was reduced from 2616 sq. km to 1633 sl.km, respectively. Error ellipse coverage was maintained at close to 90.