Identifikasi Lokasi Hiposenter Gempa Bumi Mikro menggunakan Metode Geiger dan Coupled Velocity-Hypocenter

Garini, Sherly Ardhya (2019) Identifikasi Lokasi Hiposenter Gempa Bumi Mikro menggunakan Metode Geiger dan Coupled Velocity-Hypocenter. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Distribusi dan lokasi hiposenter gempa mikro diperlukan dalam monitoring dan evaluasi kinerja reservoir panas bumi. Sehingga, lokasi hiposenter dengan keakurasian tinggi menjadi faktor yang penting untuk ditentukan. Salah satu metode yang dapat digunakan untuk mengidentifikasi lokasi hiposenter (episenter dan kedalamannya) adalah metode Geiger. Pada penelitian ini penentuan lokasi hiposenter awal (inisial) gempa bumi mikro pada area panas bumi X dilakukan dengan menggunakan metode Geiger dan relokasi lanjutan dilakukan dengan menggunakan metode Coupled Velocity-Hypocenter. Prinsip kedua metode ini adalah menghitung residual antara waktu perekaman (observed) dan waktu perhitungan (calculated). Penelitian ini menggunakan 73 data gempa bumi mikro serta 9 stasiun pengamat pada lapangan panas bumi X. Setiap data gempa mikro diklasifikasikan berdasarkan kriteria gempa bumi mikro diantaranya selisih waktu tiba (arrival time) gelombang P dan S ≤ 3 detik, magnitudo gempa ≤ 3 SR, dan setiap kejadian gempa direkam minimal oleh 3 stasiun perekam. Posisi hiposenter inisial dari pengolahan menggunakan metode Geiger kemudian di relokasi menggunakan metode Coupled Velocity-Hypocenter dengan menambahkan beberapa parameter terkoreksi seperti, model kecepatan, origin time, rasio vp/vs dan koreksi stasiun. Distribusi lokasi hiposenter gempa bumi mikro hasil relokasi menggunakan metode Coupled Velocity-Hypocenter, dengan memasukkan beberapa parameter terkoreksi lebih baik dibandingkan lokasi hiposenter gempa bumi mikro hasil metode Geiger. Hal tersebut di dukung dengan nilai RMS error rata-rata metode Coupled Velocity-Hypocenter lebih kecil (mendekati nol) yakni sebesar 0.19 detik dibandingkan dengan metode Geiger dengan rata-rata RMS error sebesar 0.74 detik. Lokasi hiposenter hasil relokasi menggunakan metode Coupled Velocity-Hypocenter lebih terkelompok di area reservoir yakni pada sumur produksi yang mengindikasikan adanya aktivitas aliran fluida melalui rekahan dari zona permeable, sedangkan pada area heat source diduga akibat dari kontak air dingin dengan batuan beku bersuhu tinggi (heat source) pada lapangan panas bumi X tersebut.
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The distribution and location of hypocenter micro-earthquakes are important factors for monitoring and evaluating the performance of geothermal reservoirs. The accuracy location of hypocenter is an important factor to determine the subsurface character beneath a geothermal area. The initial hypocenter location were determined using Geiger method and to determine the accurate location of hypocenter used Coupled Velocity-Hypocenter method. The study used 73 micro-earthquakes from 9 observer station on a geothermal area. Each micro-earthquake data is classified based on time difference between the P and S waves (ts-tp) that had values less than 3 seconds, earthquake magnitude ≤3SR and each micro-earthquake event was recorded at least by 3 observer station. Result of the initial hypocenter location from Geiger’s method were used as input to determine the accurate hypocenter location using Coupled Velocity-Hypocenter method by adding several corrected parameters, such as hypocenter location, 1-D velocity model, origin time, vp/vs ratio, zhift and the station correction. The distribution of hypocenter locations of micro-earthquakes from relocation using the Coupled Velocity-Hypocenter method, by entering several corrected parameters is better than the hypocenter location of the micro-earthquake from the Geiger method. This is supported by the average RMS error value of the Coupled Velocity-Hypocenter method which is smaller (close to zero) which is equal to 0.19 seconds compared to the Geiger method with an average RMS error of 0.74 seconds. The hypocenter location of the relocation using the Coupled Velocity-Hypocenter method is more clustered in the reservoir area which is in the production well which indicates fluid flow activity through fractures of the permeable zone, while in the heat source area it is thought to result from cold water contact with the heat source on a geothermal area.

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	Coupled Velocity-Hypocenter, Geiger, gempa bumi mikro, hiposenter, panas bumi
Subjects:	G Geography. Anthropology. Recreation > GB Physical geography > GB1197.7 Groundwater flow. Reservoirs
Divisions:	Faculty of Civil, Environmental, and Geo Engineering > Geomatics Engineering > 29101-(S2) Master Theses
Depositing User:	sherly ardhya garini
Date Deposited:	22 Jul 2026 08:40
Last Modified:	22 Jul 2026 08:40
URI:	http://repository.its.ac.id/id/eprint/69593

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