Investigation of upper crustal structure beneath eastern Java

Abstract

The complexity of geology structure in eastern Java causes this region has many potential resources as much as the disasters. Therefore, the East Java province represents an interesting area to be explored, especially regarding its upper crustal structure. To investigate this structure, we employ the Ambient Noise Tomography (ANT) method. We have used seismic waveform data from 25 Meteorological, Climatological and Geophysical Agency (BMKG) stationary seismographic stations and 26 portable seismographs installed for 2 to 8 weeks. Inter-station cross-correlation produces more than 800 Rayleigh wave components, which depict the structure beneath eastern Java. Based on the checkerboard resolution test, we found that the optimal grid size is 0.25ox0.25o. Our inversion results for the periods of 1 to 10 s indicate a good agreement with geological and Bouguer anomaly maps. Rembang high depression, most of the southern mountains zone, the northern part of Rembang zone and the central part of the Madura Island, the area of high gravity anomaly and areas dominated with igneous rocks are associated with high velocity zones. On the other hand, Kendeng zone and most of the basin in the Rembang zone are associated with low velocity zones.