TOMOGRAFI AMBIENT NOISE KECEPATAN FASE DI AREA DAERAH ISTIMEWA YOGYAKARTA DAN JAWA TENGAH; AMBIENT NOISE TOMOGRAPHY PHASE VELOCITY IN THE SPECIAL DISTRICT OF YOGYAKARTA AND CENTRAL JAVA

Saadi, Achmad G, Wiwit Suryanto

2016 | Skripsi | FMIPA

On ambient noise tomography, cross-correlation functions between two stations are applied. Because of the functions, one station acts as a virtual source and another station is a receiver. Therefore, the exact location of ambient noise source is unnecessary because it has been replaced by the location of virtual source. This method is more economic than using active source. This method is also more effective than using earthquake source, especially in low seismicity zones, due to the abundance of noise. However, when interstation distance are too close or recording time are too short, the results tend to have poor accuracy. The aim of this study is to investigate the relationship between subsurface crustal structure with respect to tectonic activities in Java, particularly in the Special District of Yogyakarta and Central Java. Additionally, since this method is fairly new, it is necessary to verify the result by comparing the tomography images from this study with the previous tomography studies. The results from this study show high velocity anomaly (3500-4400 m/s) in the fore arc of Java and low velocity anomaly (2000-2700 m/s) in the back arc of Java. The low anomaly at shallow could be due to the thick sediment layer in the Kendeng Zone and the low anomaly at depth could be due to the volcanic activities such as the rising path of magma fluids from partial melting process. The high anomaly is likely due to the subducting zone. These results correlate with the presence of low velocity anomaly Merapi Lawu Anomaly (MLA) and high velocity anomaly through prior studies that used active source and earthquake source.

Kata Kunci : ambient noise, cross-correlation, tomography, Java