Abstract Database


Johnlery Pino DEXIMO
Supervisor: Tatsuhiko HARA
Country: Philippines

The empirical distance correction function for the local magnitude, ML, scale for the Philippines was determined. We used waveform data recorded by the 12 broadband seismic stations of the Philippine Seismic Network (PSN). The used data were the maximum amplitudes measured from the simulated Wood-Anderson seismograms computed for 620 vertical component records for 81 earthquakes which occurred between 2012 and 2013. The focal depths are shallow (up to 34 km) and the hypocentral distances are in the range from 65 to 1000 km. First, we calculated ML using the IASPEI standard formula and observed a slight hypocentral distance dependence of the magnitude residuals. We performed a grid search to reduce the hypocentral distance dependence. Considering the trade-off between the coefficient n for the log (r) term and that for the r term, K, where r is the hypocentral distance, we fixed the coefficient n to 1.11 and performed a grid search for K. The obtained coefficient K is 0.00217. This is larger than that obtained for southern California, which suggests a higher dissipation of seismic wave energy in the study area. We compared local magnitude, ML estimates to those of moment magnitude, MW and duration magnitude, MD and we obtained relatively good correlations among them.