PENCITRAAN RUPTURE GEMPABUMI SUMATERA BARAT 2 MARET 2016, MW 7,9 MENGGUNAKAN METODE MUSICBP

Keywords: Sumatran Earthquake, Characteristics Rupture, Multiple Signal Back-Projection.

Abstract

Abstrak

Sumatera Barat merupakan daerah yang memiliki tingkat seismisitas sangat tinggi. Gempabumi berkekuatan besar sering melanda daerah ini baik di wilayah daratan maupun lautan. Amplitudo dari gempabumi berkekuatan besar selalu memicu terbentuknya zona segmentasi rupture. Penelitian ini bertujuan untuk menganalisis karakteristik rupture dari gempabumi M_w 7,9 yang terjadi di daerah Sumatera Barat pada tanggal 2 Maret 2016. Karakteristik dari rupture yang dihasilkan berupa nilai durasi, panjang, kecepatan, dan arah rupture. Metode yang digunakan ialah Multiple Signal Back-Projection (MUSICBP) menggunakan filter band pass dengan rentang 0,25 – 1 Hz. Data yang digunakan didapatkan dari website IRIS Wilber 3 dengan pengaturan event gempa teleseismik. Data gempabumi dengan format SAC yang digunakan direkam oleh stasiun Array Ausralia sebanyak 60 stasiun. Data SAC dari gempabumi tersebut diolah menggunakan cross correlation sehingga diperoleh sinyal yang koheren dan sefase. Hasil dari pemrosesan data berupa arah rambat rupture yang memiliki arah utara-selatan (north-south ) secara bilateral dengan panjang rupture 90 km dan berdurasi 40 detik. Gempabumi ini berjenis intraplate earthquake dengan mekanisme gempa strike slip. Selain itu, Gempabumi ini juga memiliki episenter gempa yang berada di Cekungan Wharton Samudera Hinda. Berdasarkan hasil regresi linier dari durasi dan panjang rupture maka dapat diketahui nilai kecepatan rambat rupture yaitu 2,3 km/s. Hasil pencitraan rupture gempabumi ini divalidasi menggunakan lokasi gempa susulan – gempa susulan dan didapatkan bahwa lokasi gempa susulan – gempa susulan terletak di zona segmentasi rupture gempabumi tersebut.

Kata Kunci: Gempabumi Sumatera, Karakteristik Rupture, Multiple Signal Back-Projection.    

Abstract

West Sumatra is an area that has a very high level of seismicity. Large earthquakes often hit this area both on land and sea. The amplitude of a large earthquake always triggers the formation of segmentation zone rupture. This study aims to analyze the characteristics rupture of the earthquake M_w 7.9 that occurred in West Sumatra on March 2, 2016. The characteristics of rupture the resulting are the duration, length, velocity, and direction of the rupture. The method used is Multiple Signal Back-Projection (MUSICBP) using a band pass filter with a range of 0.25 – 1 Hz. The data used is obtained from the IRIS Wilber 3 website with settings event teleseismic earthquake. Earthquake data in the SAC format used was recorded by Array 60 stations from Australia. The SAC data from the earthquake was processed using cross correlation to obtain a coherent and in-phase signal. The result of data processing is the direction of propagation rupture which has a north-south  direction bilaterally with a length of rupture 90 km and a duration of 40 seconds. This earthquake is an intraplate earthquake with an earthquake mechanism strike slip. In addition, this earthquake also has an epicenter in the Wharton Basin of the Indian Ocean. Based on the results of linear regression of the duration and length of the rupture, it can be seen that the value of the velocity rupture is 2.3 km/s. The results of imaging rupture this earthquake were validated using the location of the aftershock – aftershocks and it was found that the location of the aftershock – aftershock was located in the segmentation zone of the rupture earthquake.

Keywords: Sumatran Earthquake, Characteristics Rupture, Multiple Signal Back-Projection.