NEOTECTONIC ANALYSIS OF POHIJO-GRINDULU FAULT, PONOROGO - EAST JAVA
Muhammad Gazali Rachman, C Prasetyadi, Faiz Zain Adli
Department of Geological Engineering, UPN "Veteran" Yogyakarta
Abstract
Physiographically, Pohijo Village, Sampung District, Ponorogo Regency is located in Solo Depression Zone East Java which is near with Lawu active volcano. Administratively, Pohijo village is near from Pacitan Regency where Grindulu Active Fault is located. Girindulu fault is NE-SW oriented which continuity is not yet known until now. This research was started with desk study by learning seismicity history of the area where the research is conducted. Then, a detail observation by doing field mapping was done. Based on the field data, it was found that there is evidence which are then identified as active fault named Pohijo fault. That evidence is divided into three areas which are North area (Kruwe village, Magetan regency), Central area (Pohijo village, Ponorogo regency), and South area (Bakalan village, Wonogiri regency). In Kruwe village, an evidence in the form of abrupt terrace and landslide were found. It is predicted that those are caused by the fault of strike slip which cuts lithology in the forms of unconsolidated materials and is N 010o E oriented. In the central area, Pohijo village, landslide, road shifting, and some broken society-s houses were found. The cut lithology are in the forms of unconsolidated materials and N 035o E oriented. In South area which is located in Bakalan village, Wonogiri regency, Central Java province, there are five damaged houses, landslide, and cracked ground. The lithology which is passed by the fault is bedded clastic carbonates. Based on the evidence of the active faults found in the field, it is concluded that Girindulu fault is continuous up to the North area passing by Wonogiri regency, Ponorogo regency, and Magetan regency. Thus, mitigation disaster plan of Girindulu fault should be re-observed so that the disaster risk effect can be minimalized
Keywords: Active fault, Ponorogo, Grindulu, Earthquake mitigation
Topic: Disaster Management and Environmental Issues