Surface Geology Research and Data Analysis on Fault Creeping and Overpressure Relationship in Onshore North East Java Basin
Eri Sarmantua Sitinjak, Benyamin Sapiie, Agus M. Ramdhan

Department Geology of Institut Teknologi Bandung

Abstract

The North East Java Basin is one of the most important oil and gas basin in Indonesia. There are many manifestations of oil seeps, mud volcanoes and it is surrounded by active faults. The activity of Kendeng Fault and its relationship to overpressure and earthquake potential which will impact the oil and gas exploration or natural disaster mitigation in onshore North East Java Basin is still a question for many researchers. Therefore, a study on the quantification of fault activity and surface modelling is necessary to be done in this area, especially on fault creeping. This paper will focus on surface geological mapping data and surface modelling result based on InSAR data in defining the fault creeping and overpressure manifestation. Continues research on fault creeping has been started since 1960 in the San Andreas fault, United States. There is no continues research on fault creeping in onshore North East Java Basin or Kendeng Basin till now. The North East Java Basin or Kendeng Basin area, where many active mud volcano manifestations exist till today, is known as an area that is indeed dominated by marl and clay lithology. It is a warm basin, overpressure and an ideal environment for fault creeping to occur. We took fluid, gas, and mud samples from the mud volcanoes for laboratory analysis in order to support our justification. Diversity in its composition may be possible related to Kendeng fault activity. As most of the mud volcano manifestations in North East Java Basin or Kendeng Basin are located close to the Kendeng Fault and also related to faults as conduit to erupt to surface. From the InSAR surface modelling, we observed that there are some velocity anomalies in onshore North East Java Basin especially surround Kendeng Fault Zone. Some surface features that we suspected as a result of fault creeping were investigated and delivered in this paper. Based on this assessment we concluded that the fault creeping in onshore North East Java Basin or Kendeng Basin exist and has relationship to the overpressure manifestations in the region. The results of this research can be used for the development of oil and gas fields as well as mitigation of natural disasters that may occur related to oil and gas exploration or earthquakes.

Keywords: fault creep, mud volcano, earthquake, overpressure

Topic: Interdisciplinary Geosciences