[S03-4] Imaging of heterogeneities in the Earth with seismic scattered waves and ambient noise IV

[S03-4-06] Surface wave tomography of Java Island from ambient seismic noise

^○Sri Widiyantoro¹, Zulfakriza Zulhan¹, Agustya Martha^1,2, Phil Cummins³, Erdinc Saygin⁴, Tedi Yudistira¹, Andri Nugraha¹, Bayu Pranata^1,2, Shindy Rosalia¹ (1.Insitut Teknologi Bandung, Bandung, Indonesia, 2.BMKG, Jakarta, Indonesia, 3.Australian National University, Canberra, Australia, 4.University of Western Australia, Perth, Australia)

P- and S-wave velocity structures beneath the Sunda Arc, including Java Island, were successfully imaged in our previous studies using a global data set and a nested regional-global tomographic method. To obtain detailed crustal structure information of the region beneath Java, we have since employed the Ambient Noise Tomography (ANT) method. In this study, we have used seismic waveform data from MErapi AMphibious EXperiment (MERAMEX) in central Java and those recorded by BMKG stationary seismographic stations in Java and 25 portable seismographs, which were installed for 2 to 8 weeks in eastern and western Java. The data have been processed to obtain waveforms of cross-correlated noise between pairs of seismographic stations. Our preliminary results, for example, indicate that the Kendeng Zone, an area of low gravity anomaly extending from central to east Java, is associated with significantly lower seismic velocity than average. On the other hand, the southern mountain range, with a high gravity anomaly, is related to a high seismic velocity anomaly. We are now in the process of finishing data acquisition in western Java. The expected ANT imaging results of the whole of Java Island will be presented in the meeting. For future work, we will combine the ANT result with the mantle velocity models using body wave tomography to obtain accurate locations of earthquake hypocenters and to construct regional tectonic structures in unprecedented detail. Both of these are vital for understanding seismic hazards in Java, which is one of the most densely populated islands in the world.