ANALISIS MEKANISME FOKUS (FOCAL MECHANISM) PADA AKTIVITAS ERUPSI GUNUNG SINABUNG PERIODE BULAN JULI – DESEMBER 2013 BERDASARKAN KEJADIAN GEMPABUMI VULKANO-TEKTONIK; FOCAL MECHANISM ANALYSIS OF MT. SINABUNG ERUPTION ACTIVITY IN JULY – DECEMBER BASED ON VULCANO-TECTONIC EARTHQUAKES

Yuliantono, Ari Setiawan

2014 | Disertasi | PROGRAM STUDI S2 ILMU FISIKA

It is interesting to study the mechanisms happened in Mount Sinabung eruption in 2013 which include the hypocenter distribution and focal mechanisms. One of the ways to determine the mechanisms is through volcano-tectonic earthquakes (VT) analysis occurred. To gain this understanding, the first step is to sort the data VT from July - December 2013 from 6 stations around the mountain. Hypocenter determination in this study uses the basic method of Geiger, which is a step linearized relationship between location and time. Residual of travel time is assumed to be linear with disturbances occurred during propagation, i.e the distance between the initial hypocenter location and station. Having obtained the hypocenter, the next step is to determine the focus of each earthquake mechanism VT. A double coupling model of the input obtained from the polarity direction of the first movement of the P wave at each station is to determine the focus mechanism. From the analysis, the results show that most of the epicenter distribution occurs in northwest, north and northeast of the summit as well as a small portion evenly in the southeast and south peaks. While the dominant hypocenter distribution occurs at a depth of 3-10 km below the summit of the mountain, but there are also some hypocenter located at depths of more than 25 km. Further focal mechanism of the earthquake VT Mount Sinabung is dominated by strike-slip fault system, there is also a small portion of reverse fault system, normal faults and fault oblique. Those result show that the pressure of the supply of magma to the surface resulting earthquakes with strike-slip fault types.

Kata Kunci : Mt. Sinabung, hypocenter, epicenter, focal mechanism, volcanotectonic earthquakes, the P wave polarity, faults.