Abstract Database

RELOCATION OF LARGE EARTHQUAKES ALONG THE PHILIPPINE FAULT ZONE AND THEIR FAULT PLANES

MEE12608
Rey M. Lumbang
Supervisor: Nobuo HURUKAWA
Country: Philippines
Abstractfulltext

We relocated large magnitude (Mw 7.0) earthquakes that have occurred in the Philippine Fault Zone (PFZ) from 1900 to 2012 using the modified joint hypocenter determination (MJHD) method. In order to obtain their precise hypocenters and identify fault planes of the large earthquakes, we used P-wave arrival times at stations worldwide. We confirmed that seven earthquakes (Mw ≥ 7.0) among ten relocated large earthquakes have occurred along the PFZ, they are 1911 (Mw 7.7), 1937 (Mw 7.4), 1941 (Mw 7.0), 1947 (Mw 7.0), 1948 (Mw 7.0), 1973 (Mw 7.4) and 1990 (Mw 7.7) earthquakes. Due to the limited number of data we were unable to relocate the 1901 (Mw 7.5) earthquake. We have confirmed that the August 30, 1924 (Mw 7.1) earthquake does not belong to the PFZ, although previous studies suggested that this event had been generated by the PFZ. Referring to the epicenters of aftershocks, damaged distributions and intensity reports, we estimated the fault plane of each earthquake. In the northern PFZ, the 1990, 1937, 1901, and 1973 ruptured all part of the PFZ. In the central PFZ, only three Mw 7.0 earthquakes in 1941, 1947 and 1948 occurred. Furthermore, five 6.0 M < 7.0 earthquakes including the 2003 Masbate earthquake occurred along the PFZ. In the southern PFZ, we have only the 1911 Agusan Valley earthquake in the northern Mindanao Island.