[S01-P] Poster

[S01-P-03] Local Magnitude, ML Scale for the Philippines: Investigation of Hypocentral Distance Dependence

^○Johnlery Deximo¹, Tatsuhiko Hara² (1.Philippine Institute of Volcanology and Seismology, Department of Science and Technology (PHIVOLCS-DOST), Quezon City, Philippines, 2.International Institute of Seismology and Earthquake Engineering, Building Research Institute, Tsukuba, Japan)

We conducted a grid search for the local magnitude coefficients using broadband waveforms of local earthquakes recorded by the Philippine Seismic Network (PSN). We selected sets of the coefficients which explained the data relatively well without large hypocentral distance dependence. Compared to the distance correction functions of southern and central California and the central United States obtained from previous studies, the distance correction functions for the selected sets of the coefficients are similar to that of southern California.

To further investigate hypocentral distance dependence, we calculated the medians of local magnitude residuals for 10 bins ranging from 0 to 1000 km. When the distance correction function for southern California is used, there is a hypocentral distance dependence larger than 0.1 magnitude unit, although the scatter of the residuals is large. We show that it is possible to find local magnitude coefficients with smaller hypocentral distance dependence by a grid search.



Keywords: Local magnitude, distance correction, grid search