Source and Path Effects on Regional Phases in China

As part of the CTBT Research and Development regional characterization effort, we are assembling, organizing and analyzing geological, geophysical,and seismic data for inclusion in a knowledge base for China. We have collected seismic data from 11 Chinese Digital Seismic Network (CDSN) stations as well as IRIS stations AAK, TLY, ULN and NIL from adjoining regions. Using the published event locations and origin times, we identify Pn, Pg, Sn, and Lg phases,construct travel time curves, and estimate apparent velocities from broadband and short period seismograms. Following this, we collect amplitudes of regional seismic phases and associated noise levels using bandpassed waveforms. Studies of path specific propagation of the seismic phases have mapped blockages and have generated corrections useful in reducing scatter in magnitude estimates and in discriminant ratios. Such path corrections reduce RMS distance and mb- corrected Lg amplitude to as much as 60% of its original level (log{sub 10} domain). Path corrections are less effective with Pn data. We also study source scaling effects on these data which will allow us to refine path corrections further.