Finding Foreshock Prior To The Mw 5.6 Cianjur Earthquake Using EQTransformer

Daffa, Muhammad Afif Yusril (2025) Finding Foreshock Prior To The Mw 5.6 Cianjur Earthquake Using EQTransformer. Other thesis, Institut Teknologi Sepuluh Nopember Surabaya.

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Abstract

This study investigates foreshock sequences preceding the November 21, 2022, Mw 5.6 Cianjur earthquake in West Java, Indonesia, through deep learning methodology. Employing EQTransformer, seismogram data from 41 stations were processed to detect P and S-wave phases with probability threshold of 0.05. Phase picking accuracy was validated using Wadati diagrams, showing excellent linear correlation (R² = 0.95-0.99) with slopes of 0.67-0.72, yielding Vp/Vs ratios of 1.67-1.72, consistent with several West Java studies. And, the event was relocated using the Double Difference method. The double-difference (HypoDD) relocation method significantly improved hypocenter accuracy. Of 184 initial events, 57 were relocated with homogeneous depth distribution (9-17 km) and reduced location errors. Travel time residuals improved from ±2 seconds to nearly 0 seconds post relocation. Foreshock sequence analysis indicates the M5.6 Cianjur mainshock was not preceded by distinguishable foreshock sequences. Although seismic activity occurred around the mainshock location, its distribution lacked concentrated patterns typically associated with seismically expressed nucleation processes. The cumulative earthquake pattern showed steady increase without exponential acceleration, suggesting the mainshock rupture occurred spontaneously or through aseismic mechanisms without significant seismic precursors. This research demonstrates deep learning superiority in seismic phase detection and double-difference effectiveness for spatial clustering analysis.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	EQTransformer, Foreshocks, Microearthquake
Subjects:	Q Science > QE Geology > QE538.8 Earthquakes. Seismology Q Science > QE Geology > QE539 Microseisms.
Divisions:	Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Geophysics Engineering > 33201-(S1) Undergraduate Thesis
Depositing User:	Muhammad Afif Yusril Daffa
Date Deposited:	31 Jul 2025 09:41
Last Modified:	31 Jul 2025 09:41
URI:	http://repository.its.ac.id/id/eprint/124323

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