Neotectonic analysis of Magetan-Pacitan fault zone

Abstract

Java is an island which is considered to be quite disaster-prone. This terminology comes from the fact that along the island, we can find subduction tectonic activities which is also an epicenter. Some earthquake phenomena can be extremely destructive because of the existence of active fault as the vibration medium. Therefore, it is very important to do active fault mapping in Java island. In East Java province, there is an active fault which has been researched many times called Grindulu Fault. It is an active fault located in Pacitan Regency, East Java Province. It is a left-lateral fault. It is well exposed 500m alongside Grindulu river. However, the continuity of Grindulu northward is not well identified due to limitation of outcrop. This research was conducted to see how far the continuity of Grindulu northward. This research was started by satellite imagery survey to view areas where the existence of Grindulu fault may be found. Furthermore, field data acquisition was done on the marked areas. Field data obtained were in the form of fault slip data which were then analyzed using Wintensor software to see their kinematics. Based on the field data, the continuity of Grindulu fault can be found in three other areas which are Bakalan village, Wonogiri village; Pohijo village, Ponorogo regency; and Kruwe village, Megetan regency. Those exposed faults are strike-slip faults which are segments of massive NE-SW fault. This major fault is proposed with the name of Magetan-Pacitan active fault. The understanding of this active fault is expected to be reference for disaster mitigation in those areas.