Shear Wave Velocity Investigation for Ten Representative Sites of National Capital Territory, New Delhi, India

2011 ◽  
Vol 2 (1) ◽  
pp. 29-43 ◽  
Author(s):  
A.K. Mahajan ◽  
A.K. Shukla ◽  
Ajit Pandey ◽  
Mukesh Chauhan ◽  
Neetu Chauhan ◽  
...  
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Soft Soil ◽  
River Sediments ◽  
Soil Classification ◽  
New Delhi ◽  
Site Class ◽  
Class B ◽  
Masw Method

In this paper, shear wave velocity (Vs) investigations are carried out using Multichannel analysis of surface waves (MASW) method at ten representative sites in the NCT region, New Delhi. The analysis shows that the Vs obtained from the sites located on Alwar quartzites of Delhi Super Group ranges from 770 m/s to 2800 m/s, whereas on other sites located on lake/river sediments (Nazafgarh, Balsava and Akshar Dham) have Vs less than 180 m/s. The sites located on thick sediments shows Vs of the order of 180 m/s to 250 m/s. According to the soil classification, the sites covered can be classified under three categories: Class ‘B’ (Vs30 as >760m/s; JNU site and Asola site), class ‘D’ (Vs30>180 m/sec-360; Bhavana, Suhalpur, Ghazipur and Kirbi cantt. sites), whereas the sites located near lake/river sediments are classified as class ‘E’ (with very soft soil) and will be prone to liquefaction potential during strong earthquake shaking.

scholarly journals Estimation of hazard assessment by FINSIM for west coast and son narmada faults

2018 ◽  
Author(s):  
Shivamanth Angadi ◽  
Mayank Desai
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
West Coast ◽  
Soil Classification ◽  
Earthquake Simulation ◽  
Worst Case ◽  
Site Class ◽  
Class D ◽  
Finite Fault

Abstract. The Seismic hazard study was carried out for Maharashtra state, Bombay (Latitude 18.940 N, Longitude 72.840 E). In the present study the geological fault is known as West coast fault and Son Narmada Faults were studied and used for the earthquake simulation, extended finite fault method originally FINSIM given by M. Atkinson (1998), was used to simulate an earthquake of 6.5 Mw. The soil classification was carried out by the Shear wave velocity and the relation between Shear wave velocity and SPT valves were also recommended by Sumedh Y. Mhaske (2011), since the Mumbai has been formed by the conglomeration of various islands which has come together to form a single landmass. The soil investigation suggested that Most of the region comes under the Class D and C for the worst case simulation we have used the site class D. The peak ground accelerations (PGA) vary from 0.03g to 0.133 g. While coming to zonal area IS1893:2002 still consider the Mumbai city under zone III with the Z value of 0.16 and the result have been compared with the analysis done by many researchers in the same area.

Shear Wave Velocity- and Geology-Based Seismic Microzonation of Port-au-Prince, Haiti

2011 ◽  
Vol 27 (1_suppl1) ◽  
pp. 67-92 ◽  
Author(s):  
Brady R. Cox ◽  
Jeff Bachhuber ◽  
Ellen Rathje ◽  
Clinton M. Wood ◽  
Ranon Dulberg ◽  
...  
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Site Classification ◽  
Earthquake Hazards ◽  
Site Class ◽  
Geologic Map ◽  
Masw Method ◽  
Elevation Model ◽  
The City

A seismic site classification microzonation for the city of Port-au-Prince is presented herein. The microzonation is based on 35 shear wave velocity ( VS) profiles collected throughout the city and a new geologic map of the region. The VS profiles were obtained using the multichannel analysis of surface waves (MASW) method, while the geologic map was developed from a combination of field mapping and geomorphic interpretation of a digital elevation model (DEM). Relationships between mean shear wave velocity over the upper 30 m of the subsurface ( VS30) and surficial geologic unit have been developed, permitting code-based seismic site classification throughout the city. A site classification map for the National Earthquake Hazards Reduction Program/International Building Code (NEHRP/IBC) classification scheme is provided herein. Much of the city is founded on deposits that classify as either NEHRP Site Class C or D, based on VS30. Areas of the city requiring additional subsurface information for accurate site classification are noted.

scholarly journals Multi-method site characterization to verify the hard rock (Site Class A) assumption at 25 seismograph stations across Eastern Canada

2021 ◽  
pp. 875529302110010
Author(s):  
Sameer Ladak ◽  
Sheri Molnar ◽  
Samantha Palmer
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Hard Rock ◽  
Site Characterization ◽  
Eastern Canada ◽  
Site Class ◽  
Paleozoic Rock ◽  
Rock Types ◽  
Site Period

Site characterization is a crucial component in assessing seismic hazard, typically involving in situ shear-wave velocity ( VS) depth profiling, and measurement of site amplification including site period. Noninvasive methods are ideal for soil sites and become challenging in terms of field logistics and interpretation in more complex geologic settings including rock sites. Multiple noninvasive active- and passive-seismic techniques are applied at 25 seismograph stations across Eastern Canada. It is typically assumed that these stations are installed on hard rock. We investigate which site characterization methods are suitable at rock sites as well as confirm the hard rock assumption by providing VS profiles. Active-source compression-wave refraction and surface wave array techniques consistently provide velocity measurements at rock sites; passive-source array testing is less consistent but it is our most suitable method in constraining the rock VS. Bayesian inversion of Rayleigh wave dispersion curves provides quantitative uncertainty in the rock VS. We succeed in estimating rock VS at 16 stations, with constrained rock VS estimates at 7 stations that are consistent with previous estimates for Precambrian and Paleozoic rock types. The National Building Code of Canada uses solely the time-averaged shear-wave velocity of the upper 30 m ( VS30) to classify rock sites. We determine a mean VS30 of ∼ 1600 m/s for 16 Eastern Canada stations; the hard rock assumption is correct (>1500 m/s) but not as hard as often assumed (∼2000 m/s). Mean variability in VS30 is ∼400 m/s and can lead to softer rock classifications, in particular, for Paleozoic rock types with lower average rock VS near the hard/soft rock boundary. Microtremor and earthquake horizontal-to-vertical spectral ratios are obtained and provide site period classifications as an alternative to VS30.

scholarly journals Risks of Solely Relying on VS30 in Ground Motion Response Studies

2018 ◽  
Vol 4 (12) ◽  
pp. 2937
Author(s):  
Amin Ghanbari ◽  
Younes Daghigh ◽  
Forough Hassanvand
Keyword(s):  
Shear Wave ◽  
Ground Motion ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Ground Surface ◽  
Earthquake Excitation ◽  
Site Class ◽  
Velocity Models ◽  
Average Shear ◽  
Classification Tool

The average shear wave velocity of the uppermost 30 m of earth (Vs30) is widely used in seismic geotechnical engineering and soil-structure interaction studies. In this regard, any given subsurface profile is assigned to a specific site class according to its average shear wave velocity. However, in a real-world scenario, entirely different velocity models could be considered in the same class type due to their identical average velocities. The objective of the present study is to underline some of the risks associated with solely using Vs30 as a classification tool. To do so, three imaginary soil profiles that are quite different in nature, but all with the same average Vs were considered and were subjected to the same earthquake excitation. Seismic records acquired at the ground surface demonstrated that the three sites have different ground motion amplifications. Then, the different ground responses were used to excite a five-story structure. Results confirmed that even sites from the same class can indeed exhibit different responses under identical seismic excitations. Our results demonstrated that caution should be practiced when large-contrast velocity models are involved as such profiles are prone to pronounced ground motion amplification. This study, which serves as link between soil dynamics and structural dynamics, warns practitioners about the risks associated with oversimplifying the subsurface profile. Such oversimplifications can potentially undermine the safety of existing or future structures.

scholarly journals Struktur Kecepatan Gelombang Geser (Vs) di Daerah Rawan Gerakan Tanah (Longsor) Jalan Lintas Kabupaten Bengkulu Tengah-Kepahiang

2021 ◽  
Vol 11 (2) ◽  
pp. 134
Author(s):  
Nanang Sugianto ◽  
Refrizon Refrizon
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Velocity Structure ◽  
Soft Rock ◽  
Rock Properties ◽  
Subsurface Structure ◽  
Class D ◽  
Class B ◽  
Hard Structures

Shear wave velocity <em>(V<sub>s</sub>)</em> structure at along of Central Bengkulu-Kepahiang crossline has been mapped. This research aims to identify the subsurface structure and to estimate the constituent material type of rock in landslide-prone areas (Central Bengkulu-Kepahiang crossline). Shear wave velocity structure on each site is obtained by the HVSR-inversion of 146 microtremor data (ambient noise recording of seismometer). <em>V<sub>s</sub></em> structure at the line mapped from the surface until to 30 meters of the depth. Groups of Vs are identified in class E (<em>V<sub>s</sub></em> &lt;180), Class D (180≤<em> V<sub>s</sub></em> &lt;360), Class C (360≤<em> V<sub>s</sub></em> &lt;760), and Class B (760≤<em> V<sub>s</sub></em> &lt;1500). The subsurface structure at the depth of 0 to 10 meters are dominated by stiff soil, very dense soil, and soft rock which has highly fractured and weathered rock properties. At the depth of 15 meters to 30 meters, the subsurface structure is dominated by hard rock but it is high potential or easy to fracturing and weathering like the properties of the rocks in areas that have landslides in the past. Based on <em>V<sub>s</sub></em> value, rock constituent materials are deposition of sand, clay, gravel and alluvium ranging from soft to relatively hard structures at the depth.

scholarly journals Scholte Wave Dispersion Modeling and Subsequent Application in Seabed Shear-Wave Velocity Profile Inversion

2021 ◽  
Vol 9 (8) ◽  
pp. 840
Author(s):  
Yang Dong ◽  
Shengchun Piao ◽  
Lijia Gong ◽  
Guangxue Zheng ◽  
Kashif Iqbal ◽  
...  
Keyword(s):  
Velocity Profile ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Wave Dispersion ◽  
Dispersion Property ◽  
Scholte Wave ◽  
Shear Wave Velocity Profile ◽  
Masw Method ◽  
Low Shear

Recent studies have illustrated that the Multichannel Analysis of Surface Waves (MASW) method is an effective geoacoustic parameter inversion tool. This particular tool employs the dispersion property of broadband Scholte-type surface wave signals, which propagate along the interface between the sea water and seafloor. It is of critical importance to establish the theoretical Scholte wave dispersion curve computation model. In this typical study, the stiffness matrix method is introduced to compute the phase speed of the Scholte wave in a layered ocean environment with an elastic bottom. By computing the phase velocity in environments with a typical complexly varying seabed, it is observed that the coupling phenomenon occurs among Scholte waves corresponding to the fundamental mode and the first higher-order mode for the model with a low shear-velocity layer. Afterwards, few differences are highlighted, which should be taken into consideration while applying the MASW method in the seabed. Finally, based on the ingeniously developed nonlinear Bayesian inversion theory, the seafloor shear wave velocity profile in the southern Yellow Sea of China is inverted by employing multi-order Scholte wave dispersion curves. These inversion results illustrate that the shear wave speed is below 700 m/s in the upper layers of bottom sediments. Due to the alternation of argillaceous layers and sandy layers in the experimental area, there are several low-shear-wave-velocity layers in the inversion profile.

Sign in / Sign up

Export Citation Format

Share Document