Karakteristik Faktor Penguatan Gelombang Gempabumi oleh Lapisan Lunak Permukaan, Studi Kasus di Wilayah Perkotaan Cianjur dan Sekitarnya
DOI:
https://doi.org/10.33332/jgsm.geologi.v26i4.1009Abstract
Disamping dekat dengan sumber gempabumi,
wilayah perkotaan Cianjur juga beresiko terhadap
penguatan gelombang gempabumi oleh lapisan lunak
litologi permukaan. Endapan soil yang cukup tebal di
kawasan ini berpotensi menguatkan gelombang ketika
terjadi gempabumi. Hasil pemodelan data mikrotremor
array di 18 titik ukur diperoleh kecepatan gelombang geser
soil berkisar antara 50 m/det. - 308 m/det. Endapan soil
ini menumpang di atas batuan vulkanik yang memiliki
kecepatan gelombang geser antara 246 m/det – 1415 m/
det. Adapun ketebalan soil berdasarkan pemodelan data
mikrotremor single station di 189 titik ukur berkisar antara
2 m – 62 m. Nilai faktor penguatan gelombang oleh lapisan
soil ini berkisar antara 1 - 2,4 kali dengan zona penguatan
tinggi berada di daerah Cugenang, Warungkondang dan
Cilaku. Berdasarkan catatan, ketiga wilayah tersebut
mengalami intensitas goncangan maksimum sebesar VII
VIII skala MMI.
Kata kunci: penguatan gelombang, lapisan lunak permukaan,
mikrotremor array, mikrotremor single station.
Abstract
The Cianjur urban area is exposed to a substantial
risk, particularly near the seismic source and due to site
amplification, resulting from a soft surface layer. The fairly
thick soil deposits potentially amplify seismic waves when
an earthquake occurs. According to the microtremor array
that was deployed on 18 locations, soil shear wave velocity
ranges from 50 m/sec to 308 m/sec. This soil deposit lies
above volcanic rock that has shear wave velocities ranging
from 246 m/s to 1415 m/s. Single-station microtremor data
modelling on 189 sites revealed that the soil thickness varies
between 2 m and 62 m. The calculated site amplification of
the research area ranges from 1 to 2.4 times, indicating that
the Cugenang, Warungkondang, and Cilaku regions have
significant amplification zones. Historical records showed
that the highest shaking intensity in the three regions ranged
from VII to VIII of the MMI scale.
Keywords: site amplification, soft surface layer, array
microtremor, single station microtremor
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Copyright (c) 2025 Marjiyono Marjiyono, Hidayat Hidayat, Nimas Nurul Hamidah, Shofi Iqtina Hawan, Johannes Bosco Januar , Herry Setiawan, Shofi Andriani
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