Seismic Microzonation: A Case Study

Ansa, Atilla; Biro, Yesim; Erken, Ayfer; Gülerce, Ümit

doi:10.1007/1-4020-2528-9_9

Cited by 14 publications

(5 citation statements)

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“…Soil amplification values calculated according to Midorikawa (1987) vary between 1.5 and 2.30. On the other hand, the ground dominant periods (T 0 and MT 0 ) calculated from Vs30 and directly determined by MT (HVSR) are generally consistent, except for Malatya-1 and 2 profiles, and vary between 0.12 and 0.40 s. When evaluated according to Ansal et al (2001Ansal et al ( , 2004, these values indicate that the soil amplification and soil dominant vibration periods in the study areas are at low-medium levels. Moreover, for the soil dominant vibration period values according to Kanai and Tanaka (1961), it is defined as "rockstiff sandy gravel units" and/or "alluvium consisting of sandy-gravelly stiff clay" and is in harmony with soil classifications based on velocities obtained from seismic profiles.…”

Section: Evaluation and Interpretation Of Profilesmentioning

confidence: 61%

Subsurface characterization by active and passive source geophysical methods after the 06 February 2023 earthquakes in Turkey

Karslı,

Babacan,

Akın

2024

Nat Hazards

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Two large earthquakes (Mw = 7.7 and Mw = 7.6) that occurred in Turkey on February 6, 2023, affected a very extent region and caused a lot of loss of life and property. This paper presents preliminary results from geophysical measurements (Seismic Refraction Tomography-SRT, Multi-Channel Surface Wave Analysis-MASW and Microtremor-MT) on eight profiles in four provinces (Kahramanmaraş, Hatay, Malatya, Gaziantep) to understand the relationship between subsurface properties and the destruction that occurs immediately after earthquakes. By analyzing the geophysical data, the dynamic-elastic properties of ground and the soil classification according to Vs30 were determined. It is generally understood that the near-surface (< ~ 10–15 m) units in the measurement areas are very loose, and the deeper ones (≥ ~ 15–20 m) have a very porous/fractured structure. Soil classes were defined as ZD (Malatya-1, Hatay-1 and Kahramanmaraş-1) and ZC (Malatya-2, Hatay-2, Gaziantep-1,2 and Kahramanmaraş-2). In addition, by evaluating the information of strong ground motion station closest to the measurement profiles, it is observed that the PGA values versus epicenter distances are higher at stations in the zone parallel to the direction of both faults than those in the perpendicular zones. This leads directivity effect in the propagation of earthquake waves. The results indicate that one of the basic reasons for the damages is that the earthquake-ground-structure relationship has not been fully and accurately reflected in building designs. Therefore, future researches involving more geophysical data and PGA values will provide more information about the structural, physical and geotechnical properties of subsurface and definitive results.

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Section: Evaluation and Interpretation Of Profilesmentioning

confidence: 61%

Subsurface characterization by active and passive source geophysical methods after the 06 February 2023 earthquakes in Turkey

Karslı,

Babacan,

Akın

2024

Nat Hazards

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“…It was found that areas in the north eastern and south eastern parts of the city, with silty and clayey sand formations, have comparatively high predominant frequencies (> 4 Hz 1985, Loma Prieta 1989, Northridge 1994, Kobe 1995, Bhuj 2001, Tohoku 2011and Christchurch 2011. Local soil conditions play a significant role in the amplification of seismic waves (Street et al, 2001;Slob et al, 2002;Ansal et al, 2004). Amplification depends on the frequency of the ground motion, and younger softer soils generally amplify the ground motion more than older more competent soils or bedrock (Aki, 1993).…”

Section: Estimation Of Local Site Effects Using Microtremor Testing Imentioning

confidence: 99%

Estimation of local site effects using microtremor testing in Vijayawada city, India

Manne

Satyam

2013

Géotechnique Letters

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The microtremor method is very useful in urban areas to estimate local site effects for microzonation purposes. As seismic waves propagate from bedrock to the ground, their characteristics are site specific due to the heterogeneity of substrata. Source, path and site effects are prime parameters that affect ground response. Many destructive earthquakes that occurred in the past (e.g. Bhuj 2001, Bingol 2003, Kashmir 2005, Haiti 2010, Tohoku 2011, Van 2011 and Yunnan 2012) clearly illustrate the effects of local soils on damage severity and pattern. The Indian sub-continent has more than 400 major faults that influence seismic activity and India has experienced several devastating earthquakes (Assam 1897 (M = 8·7), Kangra 1905 (M = 8·6), Bihar-Nepal 1934 (M = 8·4), Assam-Tibet 1950 (M = 8·7), Latur 1993 (M = 6·4), Chamoli 1999 (M = 6·8), Bhuj 2001 (M = 7·6) and Sikkim 2011 (M = 6·9)). The state of Andhra Pradesh is located in the central part of peninsular India (zones II and III according to Indian seismic code) and has a record of earthquakes along the coast. This study considered Vijayawada (zone III), the third largest city in the state. Microtremor surveys were carried out at 75 different locations in the Vijayawada urban area and analysis was carried out using the Nakamura technique. Dynamic characterisation was carried out by considering the shape of the response curve, horizontal to vertical (H/V) amplitude, predominant frequency and the characteristic soil profile at all the test sites. Based on this detailed analysis, a classification is proposed and a predominant frequency map of the study area was developed. It was found that areas in the north eastern and south eastern parts of the city, with silty and clayey sand formations, have comparatively high predominant frequencies (≥ 4 Hz). The northern and western parts of the city, with high silty clay and silty sand, are characterised by moderate frequency values (2–4 Hz). Low (< 2 Hz) values of predominant frequencies were observed at a few locations. The H/V amplitudes are high (2–3) in the eastern and western regions.

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“…Conversely, formations consisting of compact and massive materials demonstrate minimal amplification or may experience wave deamplification. The phenomenon of amplification has been observed in destructive earthquakes worldwide, such as the Michoacan earthquake in Mexico (1985), Kalamata in Greece (1989), Loma Prieta in California, USA (1989), Roodbar-Manjil in Iran (1990), Kocaeli and Duzce in Turkey (1999), Chi-Chi in Taiwan (1999), Bam in Iran (2003), and Wenchuan in China (2008) [10]. This highlights the influence of lithology and rock age on seismic vulnerability in the Opak River area.…”

Section: Introductionmentioning

confidence: 99%

Microzonation of Seismic Parameters in Geological Formation Units Along the Opak River Using Microtremor Measurements

Budi Wibowo

2023

GEOMATE

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The 2006 Yogyakarta earthquake, with a magnitude of Mw 6.3, caused significant damage primarily on the west side of the Opak River. The Opak River area encompasses formations that exhibit distinct responses to seismic wave propagation. Formations consisting of unconsolidated and young sedimentary materials tend to experience wave amplification during seismic events. This study aims to investigate the seismic wave characteristics within each formation unit using microtremor measurements. The seismic wave parameters analyzed include dominant frequency, amplification factor, shear wave velocity, weathered layer thickness, seismic vulnerability index, and lithology based on N-SPT data. The study utilized 190 microtremor data sets and 7 N-SPT data sets. The microtremor data was processed using the Horizontal to Vertical Spectral Ratio Nakamura method, while the shear wave velocity data was processed using the Imai and Tonouchi approach. The findings revealed higher amplification factors in areas dominated by unconsolidated sedimentary materials and young formations. Quaternary formations are dominated by unconsolidated sedimentary material composed of sand, silt, clay, and breccia. Formations with a tertiary age are composed of more complex lithologies such as breccia-tuff, dacite tuff, andesitic tuff, volcanic breccias, lavas, siltstone, sandstone, and conglomerate. These conditions make Quaternary formations have seismic parameter characteristics such as lower dominant frequency, higher amplification factor, thicker sediment layer thickness, and higher seismic vulnerability index compared to Tertiary formations. Quaternary formations correlate with damage to buildings after the Yogyakarta earthquake, with an average shear wave velocity character of 279-293.67 m/s, and are in a zone with a vulnerability index >20. Tertiary formations demonstrated higher seismic resistance compared to Quaternary formations, indicating their relative stability.

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Seismic Microzonation: A Case Study

Cited by 14 publications

References 0 publications

Subsurface characterization by active and passive source geophysical methods after the 06 February 2023 earthquakes in Turkey

Subsurface characterization by active and passive source geophysical methods after the 06 February 2023 earthquakes in Turkey

Estimation of local site effects using microtremor testing in Vijayawada city, India

Microzonation of Seismic Parameters in Geological Formation Units Along the Opak River Using Microtremor Measurements

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