DETERMINATION OF HYPOCENTER AND SEISMIC VELOCITY STRUCTURE IN GUNTUR VOLCANO

• Main Author: BASUKI (NIM : 22412017); Pembimbing : Dr. Andri Dian Nugraha; Dr. Sri Hidayati , AHMAD
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/19838
• Institution: Institut Teknologi Bandung

Guntur is volcano-complex located in Garut district , West Java. It was very active in 19th century. In the period from 1800 to 1847, 21 eruptions occurred. The eruptions took place in short term (<12 days). The short interval of eruption was approximately 1 – 3 years, and the longest was about 6 - 7 years. Nowaday Guntur volcano has been dormant for 187 years. However increasing seismicity still occured intermittenly. In April 2013 volcanic tremor was recorded for 7 days that made increasing alert level. In September 2013, the number of Volcanic-Tectonic (VT) earthquake reach 348 events in a month. Observation on VT earthquakes in last 20 years also showed increasing number of VT-earthquake. <br /> <br /> As an effort to anticipate increasing seismicity in recent years and to monitor any changes that might happen, we conduct study on VT earthquake and seismic velocity structure under Guntur Volcano using data from January 2010 until January 2014. Earthquake hypocenter was determined using hypomh . Velocity model consist of three layers of velocity, namely 4.3 km/s on the first layer, 6.1 km/s for the second layer and 7 km/s for the third layer . The thickness of each layer is 4 km, 12 km, and 17 km. Initial velocity model then corrected using software Velest Seismic velocity structure of Vp, Vs, and the ratio Vp/Vs was calculated using Simulps12. <br /> <br /> Hypocenter distribution are clustered in three regions namely Guntur - Gandapura, Kamojang, and Darajat. The hypocenter make alignment from Gandapura to Guntur at 0-4 km depth below sea level. The location looks going deeper under Guntur Crater. The hypocenter of the earthquakes in Kamojang region were located at depth of 0-8 km below sea level, but dominantly at depth of 0-4 km. The hypocenter of the earthquakes at Darajat region were located at 0-2 km below sea level. Low velocity zone which associated with hot material or fluids was located at depth of 5 km beneath Guntur crater. Location of VT-earthquakes at depth 0 - 4 km under Guntur Crater was coincide with the area with high Vp and Vs.