Perbaikan Model Kecepatan Seismik 1-D Dan Relokasi Hiposenter Gempa Di Selat Sunda

Edelo, Arham Zakki (2021) Perbaikan Model Kecepatan Seismik 1-D Dan Relokasi Hiposenter Gempa Di Selat Sunda. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Model kecepatan berperan sangat penting dalam proses relokasi hiposenter. Model global yang rutin digunakan pada relokasi gempa pada umumnya tidak selalu sesuai dengan kondisi sebenarnya, sehingga menghasilkan posisi hiposenter yang tidak akurat. Pada penelitian ini dilakukan perbaikan terhadap model kecepatan 1-D Gelombang P (Vp) di Selat Sunda dan area sekitarnya menggunakan program VELEST. Data waveform yang digunakan adalah hasil rekaman selama periode 2015 – 2020 dan diunduh melalui laman WebDC3. Kemudian posisi hiposenter awal ditentukan dengan program NonLinloc menggunakan data picking manual arrival time P dan S. Penentuan hiposenter awal menghasilkan 68 event gempa dengan 301 fase untuk masing-masing gelombang P dan S. kemudian perhitungan model kecepatan 1-D Vp dilakukan dengan menggunakan tiga pendekatan yaitu Low Vp. Intermediate Vp, dan High Vp. Hasil perhitungan VELEST menunjukan model final High Vp dengan nilai kecepatan 3,93 – 5,99 km/s pada kedalaman 0 – 30 km dan 8,93 – 8,98 km/s pada kedalaman 30 – 260 km memiliki stabilitas terbaik yang kemudian digunakan sebagai model kecepatan pada proses relokasi menggunakan program hypoDD dengan menerapkan algoritma double-difference. Dari total 68 event gempa awal hasil penentuan menggunakan NonLinLoc, 41 gempa berhasil direlokasi dengan variasi kedalaman dan akurasi posisi yang lebih baik. Hasil relokasi menghasilkan nilai RMS error dominan berada pada rentang antara 0 – 0,9 detik, sementara nilai waktu tempuh residual dominan berada pada rentang 0 – 2 detik. Hiposenter hasil relokasi menunjukan mayoritas kejadian gempa merupakan gempa dalam yang berasosiasi dengan zona subduksi. Sementara gampa dangkal di zona kerak diduga terjadi akibat aktivitas sesar yang masih berasosiasi dengan zona subduksi utama.
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The velocity model is very important in the hypocenter relocation study. Global
models that are routinely used in earthquake relocation generally do not always
match the actual conditions, resulting in inaccurate hypocenter positions. In this
study, improvements were made to the 1-D P-Wave velocity model (Vp) in the
Sunda Strait and surrounding areas using the VELEST program. The waveform
was recorded during the 2015 - 2020 period and downloaded from the WebDC3
webpage. Then, the initial hypocenter was determined by the NonLinloc program
using manual data picking of P and S arrival times. Determination of the initial
hypocenter resulted in 68 earthquake events with 301 phases for each P and S
wave. Then the calculation of the 1-D Vp velocity model was carried out using
three approaches which are Low Vp, Medium Vp, and High Vp. The results of
the VELEST calculation show that the final High Vp model with velocity value
of 3.93 - 5.99 km/ s at a depth of 0 - 30 km and 8.93 - 8.98 km/s at a depth of 30
- 260 km have the best stability. This final High Vp then used as a velocity model
in the relocation process using the hypoDD program by applying a double�difference algorithm. From a total of 68 earthquake events determined by
NonLinLoc, 41 earthquakes were successfully relocated with more variations in
depth and better accuracy. The relocation resulted in the dominant RMS error
value being in the range of 0 - 0.9 seconds, while the dominant residual travel
time value was in the range of 0 - 2 seconds. The relocated hypocenter showed
that most earthquake events were deep earthquakes that associate with the
subduction zone. Meanwhile, shallow earthquakes in the crustal zone are
assumed to occur due to faults activity that still associates with the subduction
zone.

Item Type:	Thesis (Undergraduate)
Uncontrolled Keywords:	Model 1-D, hiposenter, double-difference, Selat Sunda, Relokasi
Subjects:	Q Science > QE Geology > QE538.8 Earthquakes. Seismology
Divisions:	Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Geophysics Engineering > 33201-(S1) Undergraduate Thesis
Depositing User:	Arham Zakki Edelo
Date Deposited:	02 Sep 2021 07:42
Last Modified:	02 Sep 2021 07:42
URI:	http://repository.its.ac.id/id/eprint/90481

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