Seismic microzonation by using microtremor method in Pandan volcano, Bojonegoro, East Java

Abstract

Pandan volcano geographically is located in the north of Madiun and Nganjuk district, and south Bojonegoro district. The status of this volcano is longer not active, but it still emerges hot spring in some areas. This research aims to understand the distribution of the natural frequency value, the amplification factor value, and the vulnerability index value by using mictrotremor horizontal to vertical spectrum ratio (HVSR) method, that is believed to have an important contribution to earthquake disaster mitigation. There are 19 measurement sites where geographically ranges between 7°26′36.60″–7°27′16.49″S and 111°46′31.76″– 111°47′11.98″E. The survey used portable seismograph 3-components SL07 SARA single station. For each site of measurement needs 30 minutes of ambient noise recording with a sampling rate of 100 Hz. The data processing was done by HVSR analysis method on Easy HVSR software. The natural frequency (fo) value ranges between 1,1 and 9,95 Hz, and amplification factor (Ag) value varies from 2,1 to 7,2. The vulnerability index (Kg) value ranging from 0,48 to 25,34. The highest risk index is located in the north part of the research area where have high potential to damage when the earthquake happens.