Preliminary site characteristics for urban seismic hazard in pasuruan fault from microtremor measurements

A student training program, Engineering Seismology and Seismic Microzonation for Seismic Site Effects Assessment, was held 18–22 January 2020 in Lalitpur, Nepal. It was created through the collaboration of Thammasat University and Tribhuvan University, with support from Geoscientists Without Borders® (GWB). The goal of the program was to connect students with modern geophysical instrumentation and software through training. It specifically advanced theoretical and hands-on field-based knowledge pertaining to geotechnical earthquake engineering aspects and applications. The training served as part of a broader GWB project, Seismic Site Effects Study in Nepal, encompassing basin geometry, site characteristics, and the study of seismic site effects through microtremor measurements in Kathmandu Valley.

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Determination of path attenuation and site characteristics of the North-west Himalayan region and adjoining regions within the Indian Territory using Generalized inversion method

Annals of Geophysics ◽

10.4401/ag-8225 ◽

2020 ◽

Vol 63 (6) ◽

Author(s):

Nelliparanbil Harinarayan ◽

Abhishek Kumar

Keyword(s):

Seismic Hazard ◽

Predominant Frequency ◽

Site Class ◽

North West ◽

The North ◽

Generalized Inversion ◽

Site Characteristics ◽

Generalized Inversion Technique ◽

Recording Station

North-west Himalayas and its adjoining regions have been experiencing deadly earthqaukes from time to time and are home for a large portion of population of Indian subcontinent. Knowledge of regional path attenuation and site parameters are prerequisite while attempting seismic hazard studies towards minimizing damages during future earthqaukes for a region. Present work focuses on the determination of path attenuation and site characteristics of earthqaukes recording stations, located in the north-west Himalayas and its adjoining regions, within India. It is done using two- step generalized inversion technique. In the first step of inversion, non-parametric attenuation curves are developed by constraining attenuation to be a smooth decaying function with hypocentral distance. Qs = (105 ± 11)f (0.94 ± 0.08) as S wave quality factor is obtained indicating that the region is seismically active having high degree of heterogeneities in the crustal medium. In the second step of generalized inversion, site amplification curve, at each recording station, is computed as the ratio of site spectral amplitude of horizontal and vertical components. In addition, based on Horizontal to vertical spectral ratio (HVSR) method, predominant frequency of each recording station is calculated. Values of predominant frequencies based on HVSR and generalized inversion are found matching for each of the recording station. Based on obtained predominant frequency, site class of 101 recording stations, which at present are absent, are determined in this work. Determined path attenuation as well as site parameters can be collectively used for developing regional ground motion models and subsequently for seismic hazard studies for the selected region.

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Spectral Estimation of Site Characteristics of an Earth Quake Prone Region

10.21203/rs.3.rs-623385/v1 ◽

2021 ◽

Author(s):

T. Seshunarayana ◽

N. Sundararajan

Keyword(s):

Seismic Hazard ◽

Shear Wave ◽

Wave Velocity ◽

Shear Wave Velocity ◽

Earth Quake ◽

Ambient Noise ◽

Site Amplification ◽

Time Data ◽

Ground Shaking ◽

Site Characteristics

Abstract The site amplification characteristic is an important part of evaluation of seismic hazard since much of the damage caused by earthquakes may be attributed directly to the ground shaking. Identifying ahead of time such areas which are prone to amplified ground shaking due to earthquake could greatly aid seismic hazard evaluation as well as improved hazard mitigation effects. It is also a well known fact that in most cases site amplification/ shaking is stronger in low shear wave velocity areas. The objective of the present study is to estimate site characteristics of as many as 116 sites in an area of approximately 35 sq.km comprising various geological units including soft alluvial deposits which not only tend to amplify certain frequencies of ground motion but also extend the duration of earth quake that may cause further damage. The basic idea of this study is to decipher the natural ground response during quite period as well as triggered response by spectral analysis. The methodology adopted for the study is modified micro tremor which is based on ambient noise as well as triggered response. Further, the spectral ratio of H/V of ambient noise and triggered data by Nakamura method with short duration data were also estimated. In addition, based on some empirical relations, the site response frequency and amplification were also computed using the shear wave velocity obtained up to a depth of 30 m (VS30) by the method of multichannel analysis of surface wave (MASW) and depth to bed rock estimated through refraction seismic studies. The results of the study has shown that a simple comparison of spectra of quiet time data and triggered time data revealed that in alluvial soils with thick overburden, the signal amplification is more at low frequency (< 10 Hz), whereas in thin overburden the amplification was found to be low at low frequencies. The salient features of the study with merits are presented herein.

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Microtremor measurements in the India's holy city, Varanasi for assessment of site characteristics

Quaternary International ◽

10.1016/j.quaint.2021.01.008 ◽

2021 ◽

Author(s):

Uma Shankar ◽

Sangeeta Kumari ◽

Pawan Kumar Yadav ◽

A.P. Singh ◽

Arun Kumar Gupta

Keyword(s):

Site Characteristics ◽

Microtremor Measurements ◽

Holy City

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PEMETAAN DAERAH RENTAN GEMPA BUMI SEBAGAI DASAR PERENCANAAN TATA RUANG DAN WILAYAH DI PROVINSI SULAWESI BARAT

KURVATEK ◽

10.33579/krvtk.v1i2.417 ◽

2017 ◽

Vol 1 (2) ◽

pp. 41-47

Author(s):

Marinda noor Eva

Keyword(s):

Seismic Hazard ◽

Hazard Analysis ◽

Probabilistic Seismic Hazard Analysis ◽

Seismic Hazard Analysis ◽

Probabilistic Seismic Hazard

Penelitian mengenai daerah rawan gempa bumi ini menggunakan Metode Probabilistic Seismic Hazard Analysis (PSHA) di Provinsi Sulawesi Barat, dengan tujuan untuk memetakan tingkat kerawanan bahaya gempa bumi di Kabupaten Mamasa. Penelitian ini menggunakan data kejadian gempa bumi di Pulau Sulawesi dan sekitarnya dari tahun 1900 – 2015. Hasil pengolahan PSHA menggunakan Software Ez-Frisk 7.52 yang menghasilkan nilai hazard di batuan dasar pada kondisi PGA (T = 0,0 sekon), dengan periode ulang 500 tahun dan 2500 tahun berkisar antara (149,54 – 439,45) gal dan (287,18 – 762,81) gal. Nilai hazard di batuan dasar dengan kondisi spektra T = 0,2 sekon untuk periode ulang 500 tahun dan 2500 tahun adalah (307,04 – 1010,90) gal dan (569,48 – 1849,78) gal. Nilai hazard di batuan dasar dengan kondisi spektra T = 1,0 sekon untuk periode ulang 500 tahun dan 2500 tahun diperoleh nilai (118,01 – 265,75) gal dan (223,74 – 510,92) gal. Berdasarkan analisis PSHA, nilai PGA di Provinsi Sulawesi Barat dominan dipengaruhi oleh sumber gempa sesar.

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