Studi Relokasi Hiposenter Aftershock Gempa Yogyakarta 2006

Abstract

Studi relokasi hiposenter aftershock gempa Yogyakarta 2006 telah diteliiti melalui pengolahan data waveform aftershock gempa Yogyakarta pada 16 Juni s.d 5 Juli 2006.  Data model kecepatan gelombang 1D Jawa Tengah digunakan sebagai model kecepatan awal. Identifikasi distribusi hiposenter gempa bumi diperoleh menggunakan metode Joint Hypocenter Determination (JHD) dan program Velest. Lokasi hiposenter ini selanjutnya di plot pada peta menggunakan GMT (Generic Mapping Tools). Hasil penelitian memperlihatkan bahwa persebaran hiposenter gempabumi membentuk tiga buah cluster, berada dibagian timur kemudian membelok ke arah selatan Sesar Opak. Hiposenter memiliki pola persebaran membentuk suatu bidang sesar. Kemudian, hasil penelitian menemukan adanya rambatan energi di sepanjang zona lemah Sesar Opak dari sesar aktif di bagian timur. Nilai RMS residual relokasi hiposenter  menunjukkan hasil yang cukup akurat yaitu sebesar 0,0596 detik dan menghasilkan model kecepatan yang tidak jauh berbeda dengan model kecepatan awal (Jawa Tengah).

The relocation study of the 2006 Yogyakarta earthquake aftershock hypocenter has been investigated through the processing of the Yogyakarta earthquake aftershock waveform data from 16 June to 5 July 2006. Data from the 1D wave velocity model of Central Java is used as the initial velocity model. Identification of the earthquake hypocenter distribution was obtained using the Joint Hypocenter Determination (JHD) method and the Velest program. The hypocenter location is then plotted on the map using GMT (Generic Mapping Tools). The results showed that the hypocenter of the earthquake formed three clusters, located in the eastern part and then veered to the south of the Opak Fault. The hypocenter has a distribution pattern to form a fault plane. Then, the results of the study found energy propagation along the weak zone of the Opak Fault from an active fault in the eastern part. The RMS value of the residual hypocenter relocation shows a fairly accurate result of 0.0596 seconds and produces a velocity model that is not much different from the initial velocity model (Central Java).