3D VELOCITY MODEL OF PAPANDAYAN VOLCANO WEST JAVA USING DELAY TIME TOMOGRAPHY METHOD

Abstract

Papandayan volcano in West Java is one of the volcanoes in Indonesia. In history, Papandayan volcano it had erupted in 1772, 1923, 1942 and 2002. The eruption period in 2002 had stopped, but Papandayan volcano still shows high volcano-tectonic (VT) activities. The activity also followed increasing in status into “siaga” level occurred in 2010, 2011, 2012 and 2012. So, for knowing 3D velocity model that representation of the hot area or weak, we need to had been a research of delay time tomography.

The research used volcanic earthquake data by recorded from 5 permanent stations and 5 temporary stations. The data processing had been set earthquake type and picking arrival time from VT earthquake. We input arrival time to knowing hypocenter by Geiger method. We get the velocity variation from matrix inversion by least square method. The input of least square inversion used delay time from the difference between travel time of observation and calculation.

The research has shown that hypocenter of VT earthquake line under Mas crater at depth 1 km above mean sea level (MSL) to 5 km beneath MSL. Inversion of tomography has been shown anomaly zone of low velocity in depth 5 km beneath MSL. This zone associated with VT earthquake location. It has physics characteristic such brittle, heterogenic, and hot. The anomaly zone can be interpreted as the hot material zone which associated with a residue of shallow magma chamber or effect of volcanic-tectonic activities from a long time ago.