PENENTUAN SEBARAN HYPOCENTER PADA SAAT PROSES PEMBENTUKAN KUBAH LAVA MERAPI PERIODE BULAN MARET SAMPAI DENGAN APRIL TAHUN 2006

Abstract

The purpose of this research is to determine hypocenter distribution or focus of earthquake on the subsufrace of Merapi volcano at the period of the growth of lava dome process in March until April on 2006. This research has been done at Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian (BPPTK) at Yogyakarta form 2008 May of 5th until 2008 August of 8th. The result of this research can used to be early warning system, such as estimating the direction of lava dome’s fall down To know hypocenter distribution from volcanic earthquake record of Merapi the simplex optimization method in the Hyposymx software can be used, where hypocenter determined from calculation of error value from the differences between P and S wave’s arrival time observed and arrival time calculated from all seismic station around Merapi, those are Pusunglondon, Klatakan, Deles and Plawangan. Each point of hypocenter is point that has the most little error value after the iteration in Hyposimx software. The result of this research is hypocenter distribution around Merapi crater with the direction are located at west of Merapi crater which the coordinate is 436000 to 441500 and 9161200 to 9170400 in UTM of from 110,42°E to110,48°E and 7,49°S to 7,58°S. The range of hypocenter’s depth are from 699 m until 1799 m in March and from 239 until 1499 m in April.