Research for the Volcanic and Seismic Activity in Luzon

点击翻译按钮获取中文摘要

1) The Macolod Corridor in Southwestern Luzon is an approximately 40 km wide zone of active intense Quaternary volcanism which crosses perpendicular the Island in a NE-SW direction and this zone is considered to be a pull-apart rift zone. In order to determine the displacement velocity of crustal movement in Macolod Corridor, GPS measurements were executed. Thirteen stations were established in Luzon, Mindoro, and Marinduque islands during observation period in April and September, 1996. A 24 hours continuous measurement was made for 3-6 days at each station with a rate of one sample per 30 seconds. After a baseline analysis including data at Manila, IGS station, we got a displacement velocity in and around the Macolod Corridor, which shows such a large value as 2 cm/year. To check whether this value includes some errors caused by vapor in atmosphere, we executed a GPS measurement at 9 stations in January and February, 1997 with a observation period of 5 days.2) To check the presence of a slab between the Manila and the Negros trenches, we installed 9 seismic stations in Luzon, Mindoro, Marinduque, Tablas, Sibuyan and Panay islands and seismic activity in this region was monitored. Distances between stations varied from 60 to 90 km. However, during the nine-month observation period, only local seismicity around some stations were directed and we could not get a hypocenter along a subducting slab because of short period observation, low seismicity, and some technical problems like power failure.3) In order to study pre-calderagenic eruption material and history of magma plumbing system in the Macolod Corridor, we collected volcanic rock samples around Taal volcano, a large caldera volcano, and Lagna de Bay. Petrological and Geochronological study were started such as trace element analysis and K-Ar dating.