RELOKASI HIPOSENTER GEMPA VULKANIK GUNUNGAPI LOKON SULAWESI UTARA MENGGUNAKAN KOREKSI MODEL KECEPATAN 1-D STUDI KASUS SEPTEMBER-DESEMBER 2012; HYPOCENTER RELOCATION OF VOLCANO EARTHQUAKES BENEATH LOKON VOLCANO NORTH SULAWESI USING 1-D VELOCITY MODEL CORRECTION CASE STUDY SEPTEMBER-DECEMBER 2012

ARDIANI, MEI ASTRID, Wiwit Suryanto

2016 | Skripsi | FMIPA

Lokon volcano is one of five active volcanoes in North Sulawesi. This volcano was located near from residential areas, so this research of characteristic of this volcano be required. One of the way is calculation of hypocenter. Calculation of 1-D velocity model correction to relocate hypocenter distribution has been done too. This calculation has been done because the local velocity model information of Lokon volcano not yet known. Hypocenter relocation using 1-D velocity model correction is calculated using Local Earthquake Tomography Method in a way to reduce the value of RMS error of initial hypocenter calculation. The value of RMS error are obtained from root mean square of latitude, longitude and altitude error. The hypocenter data is calculated by using Geiger Method from picking result of P wave and S wave in seismogram. The seismogram data was acquired from five seismic station located around Lokon volcano. Vp/Vs input ratio was 1.73 for each layer. Velocity model estimation after correction reduce the error RMS value. The value of RMS error average before the correction is 0.25 second, while the value of RMS error average after correction changed into 0.11 second Hypocenter distribution after correction spread around Tompaluan crater, the center of volcanic activity of Lokon volcano at this time. Hypocenter depths tend to be at depth of 0.87 km above mean sea level to 2.94 km below mean sea level. Earthquakes with depth less than 2 km includeded in shallow earthquakes. Shallow earthquakes occured due to an increase in vulcanic activity. While for deep earthquakes, which is an earthquake with depth more than 2 km, only several are identified. The hypocenter distribution during this last four months shows no movement pattern of magma to the surface on regular basis.

Kata Kunci : 1-D velocity model, volcano earthquakes, relocation, Lokon volcano.