Influence of local site conditions on strong ground motion characteristics at Tarai region of Uttarakhand, India

Pandey, Bhavesh; Jakka, Ravi S.; Kumar, Ashok

doi:10.1007/s11069-015-2120-0

Cited by 37 publications

(9 citation statements)

References 7 publications

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“…A particular region of Garhwal-Kumaun Himalaya is called the 'central seismic gap (CSG)', which has the potential to generate large earthquakes in the near future (Bilham et al 2001). Also, the Indo-Gangetic plain in Northern India contains the highest population density in India (Pandey et al 2016), posing a severe threat to people from any expected earthquake. Another critical factor is that the Indo-Gangetic plain contains deep alluvial deposits, which significantly modify the incoming seismic ground motions (Jakka et al 2015).…”

Section: Real Case Studymentioning

confidence: 99%

Use of a-priori information to minimize uncertainties in surface wave inversion and subsequent site response analysis

Desai

Jakka

Foti

2022

Preprint

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Multi-channel analysis of surface waves (MASW) is the most popular method to estimate the shear wave velocity (Vs) profile of soil and subsequently, the seismic site response. Nevertheless, the inversion process to retrieve the Vs profile from MASW testing is inherently ill-posed and non-unique, inducing considerable uncertainties in the results. Also, using nonlinearity curves without knowing the soil type leads to further uncertainties in site response analysis (SRA) results. Despite several efforts by researchers, the uncertainties in MASW testing and subsequent SRA still remain a matter of obvious concern in earthquake engineering. In this study, an attempt has been made to investigate how these uncertainties can be tackled by utilizing a-priori information from geotechnical investigations. The type of a-priori information used in this work is the number and thickness of soil layers, soil type, and index properties. Initially, a numerical study was carried out using simulations of MASW and SRA for nine possible types of idealized Vs profiles using three different types of earthquake motions. Then, a field MASW test, borehole drilling, sampling and SRA were carried out at a site in Roorkee, India. Statistical properties of the results without and with a-priori information were determined and compared. It was found that for any type of Vs profile or seismic motion, the use of a-priori information significantly mitigates the inversion uncertainty in MASW and SRA, thereby remarkably enhancing the reliability and accuracy of the MASW and SRA results. This work also provides a quantitative assessment of the uncertainty reduction using a-priori information for different possible site and earthquake scenarios, which would help understand the need for a-priori information with MASW testing.

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Section: Real Case Studymentioning

confidence: 99%

Use of a-priori information to minimize uncertainties in surface wave inversion and subsequent site response analysis

Desai

Jakka

Foti

2022

Preprint

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“…Mahajan et al (2011) have conducted studies on characterization of sediments in the Himalayan foothills using both active and passive MASW techniques. More recently, Pandey et al (2016) carried out extensive MASW studies for quantifying the influence of local site conditions on strong ground motions. MASW is a well-accepted and widely used method for seismic microzonation studies.…”

Section: Multichannel Analysis Of Surface Waves (Masw)mentioning

confidence: 99%

Estimation of bedrock depth for a part of Garhwal Himalayas using two different geophysical techniques

et al. 2018

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It has now been well established that the depth of bedrock is a key parameter in assessing the impact of local site conditions on seismic hazard analysis. Where conventional geotechnical testing like standard penetration test (SPT) or cone penetration test (CPT) requires a far greater cost and manpower to be used for such purposes, geophysical testing like ground-penetrating radar (GPR) and multichannel analysis of surface waves (MASW) may provide the researchers with more viable options to achieve conclusive evidence on bedrock depth. Application of geophysical techniques has become more and more extensive and advanced in many geo-morphological studies since the early 2000s. Geophysical techniques require less time and effort, and the easy processing of the obtained data is the primary reason for their popularity. However, due to variability in subsoil mechanical properties, wave attenuation and dispersion and diverse geological boundary conditions, the results obtained through geophysical techniques are often ambiguous and non-unique. The interpretation of the obtained data also requires skill and experience, as the range may vary widely and more often than not consensus is difficult to achieve. In this paper, an endeavor has been made to coalesce the results of two widely used geophysical techniques, namely GPR and MASW to derive more conclusive evidence for the detection of bedrock depth in a part of Garhwal Himalayas. The study area comprises of two different cities of Uttarakhand, India. Both the sites possess different geo-morphological attributes and thus prove to be a perfect platform to conduct the experimentations. Both GPR and MASW testing have been performed and results are shown in graphical format. A comparison of the GPR survey with a conventional geotechnical testing (SPT) is also presented here. This study shows that GPR and MASW can provide complementary results in estimating bedrock depth.

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“…Hartzell [12] studied the influence of topography on ground motion and evaluated topographic amplification utilizing a variety of methods. Pandey [13] discussed the influence of local site conditions on the characteristics of strong ground motion records, and their further effects on hazard studies have been investigated. Tran et al [14] discussed the influence of random variations in soil characterization on seismic site response.…”

Section: Introductionmentioning

confidence: 99%

Seismic response analysis of loess site under far-field bedrock ground motion of the Wenchuan earthquake

Chen

2021

PLoS ONE

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In this paper, considering the far-field seismic input, an accelerogram recorded in the bedrock at Wuquan Mountain in Lanzhou city during the 2008 Wenchuan Ms8.0 earthquake was selected, and numerical dynamic analyses were conducted. The one-dimensional equivalent linear method was implemented to estimate the ground motion effects in the loess regions. Thereafter, slope topographic effects on ground motion were studied by applying the dynamic finite-element method. The results revealed the relationship between the PGA amplification coefficients and the soil layer thickness, which confirmed that the dynamic response of the sites had obvious nonlinear characteristics. The results also showed that there was an obvious difference in the dynamic magnification factor between the short-period and long-period structures. Moreover, it was found that the amplification coefficient of the observation point at the free surface was greater than the point inside the soil at the same depth, which mainly occurred in the upper slope. Through this study, the quantitative assessment of ground motion effects in loess regions can be approximately estimated, and the amplification mechanism of the far-field ground motion mechanism can be further explained. In addition to the refraction and reflection theory of seismic waves, the resonance phenomenon may help explain the slope topographic effect through spectrum analysis.

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Influence of local site conditions on strong ground motion characteristics at Tarai region of Uttarakhand, India

Cited by 37 publications

References 7 publications

Use of a-priori information to minimize uncertainties in surface wave inversion and subsequent site response analysis

Use of a-priori information to minimize uncertainties in surface wave inversion and subsequent site response analysis

Estimation of bedrock depth for a part of Garhwal Himalayas using two different geophysical techniques

Seismic response analysis of loess site under far-field bedrock ground motion of the Wenchuan earthquake

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