scholarly journals Near-surface seismic refraction tomography and MASW for site characterization in Phuentsholing, Bhutan Himalaya

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Raju Sarkar ◽  
Sreevalsa Kolathayar ◽  
Dowchu Drukpa ◽  
Kinley Choki ◽  
Shrijana Rai ◽  
...  
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Seismic Refraction ◽  
P Wave ◽  
Response Analysis ◽  
Soil Parameters ◽  
Near Surface ◽  
Engineering Construction ◽  
Refraction Tomography

AbstractIt is essential to understand the soil characteristics of the subsurface layers for any engineering construction. In difficult terrains like hilly areas, conventional methods of investigation are expensive and difficult to conduct. It calls for nondestructive testing methods to get reliable estimates of subsurface properties. In the present study, seismic refraction tomography (SRT) technique and multichannel analysis of surface waves (MASW) methods were carried out along five selected profiles in Phuentsholing region of Bhutan Himalaya. The profile length ranges from 37 to 81.5 m, and depth of imaging down to 10 m. While the SRT data imaged the P-wave velocity (Vp) structures, the MASW imaged the shear wave velocity (Vs) structures. The P-wave images provide a fair knowledge of geological layers, while the MASW images provide S-wave velocity structures (Vs). These results are useful to estimate soil parameters, like the density, Poisson’s ratio, Young’s modulus, shear modulus, N-value and the ultimate bearing capacity. The seismic images reveal the presence of sand, sandy clay, gravels and shale layers below the selected sites. Bhutan Himalayas being seismically vulnerable, the obtained results in terms of shear wave velocity were accustomed to categorize the sites as per NEHRP site classes, and a ground response analysis was performed to determine the reliable amplification factors. From the study, it is suggested that the engineering construction is feasible at all the sites except in one site, where an indication of saturated soil is observed which is vulnerable for liquefaction, and ground needs to be improved before construction at that site.

scholarly journals Near surface shear wave velocity in Bucharest, Romania

2008 ◽  
Vol 8 (6) ◽  
pp. 1299-1307 ◽  
Author(s):  
M. von Steht ◽  
B. Jaskolla ◽  
J. R. R. Ritter
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Seismic Velocity ◽  
Seismic Refraction ◽  
Compressional Wave ◽  
Seismic Zone ◽  
Surface Shear ◽  
Near Surface ◽  
Surface Shear Wave

Abstract. Bucharest, the capital of Romania with nearly 2 1/2 million inhabitants, is endangered by the strong earthquakes in the Vrancea seismic zone. To obtain information on the near surface shear-wave velocity Vs structure and to improve the available microzonations we conducted seismic refraction measurements in two parks of the city. There the shallow Vs structure is determined along five profiles, and the compressional-wave velocity (Vp) structure is obtained along one profile. Although the amount of data collected is limited, they offer a reasonable idea about the seismic velocity distribution in these two locations. This knowledge is useful for a city like Bucharest where seismic velocity information so far is sparse and poorly documented. Using sledge-hammer blows on a steel plate and a 24-channel recording unit, we observe clear shear-wave arrivals in a very noisy environment up to a distance of 300 m from the source. The Vp model along profile 1 can be correlated with the known near surface sedimentary layers. Vp increases from 320 m/s near the surface to 1280 m/s above 55–65 m depth. The Vs models along all five profiles are characterized by low Vs (<350 m/s) in the upper 60 m depth and a maximum Vs of about 1000 m/s below this depth. In the upper 30 m the average Vs30 varies from 210 m/s to 290 m/s. The Vp-Vs relations lead to a high Poisson's ratio of 0.45–0.49 in the upper ~60 m depth, which is an indication for water-saturated clayey sediments. Such ground conditions may severely influence the ground motion during strong Vrancea earthquakes.

Topographically-Derived Near-Surface Shear Wave Velocity Map for Pakistan

2017 ◽  
Vol 11 (02) ◽  
pp. 1650010 ◽  
Author(s):  
Saeed Zaman ◽  
Pennung Warnitchai
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Site Response ◽  
Response Analysis ◽  
Site Classification ◽  
Site Conditions ◽  
Data Set ◽  
Near Surface ◽  
Topographic Slope

Shear wave velocity ([Formula: see text]) through the uppermost subsurface (30 m) is usually considered an important parameter as it dictates the dynamic behavior of soil and also acts as an input parameter for site response analysis, seismic hazard analysis, and site classification. In majority of seismically active areas across the globe, especially in developing countries like Pakistan, the [Formula: see text] measurements are either not available or if available, they are very limited in number to develop a seismic site-conditions map. In the absence of proper geological studies and geotechnical investigation, the slope-derived method provides a simple solution to map the site-conditions. The current study presents the development of slope-derived [Formula: see text] map on the basis of a correlation between [Formula: see text] and topographic slope for active tectonic regions and its comparison with the [Formula: see text] values at various locations in Pakistan. The topographic slope is calculated from digital elevation model (CDEM) of the Shuttle Radar Topography Mission (SRTM) 30 arc-sec global topographic data set. The [Formula: see text] values comprise of directly available, values calculated/estimated from the standard penetration tests (SPTs [Formula: see text]-value) and primary waves at various locations in Pakistan. [Formula: see text] values at various parts/locations in Pakistan and values from the slope-derived [Formula: see text] map are found to be fairly comparable and based on these results for seismically active areas like Pakistan, slope-derived method can be applied for the first-order site-condition studies.

Estimating Near-Surface Shear Wave Velocity Using the P-Wave Seismograms Method in Japan

2018 ◽  
Vol 34 (4) ◽  
pp. 1955-1971 ◽  
Author(s):  
Yu Miao ◽  
Yang Shi ◽  
Su-Yang Wang
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Polynomial Regression ◽  
Empirical Relationship ◽  
Theoretical Method ◽  
P Wave ◽  
Surface Shear ◽  
Near Surface ◽  
Surface Shear Wave

Using initial P-wave records at 298 seismic stations from the Kiban-Kyoshin network (KiK-net), the P-wave seismograms method is employed to estimate the near-surface shear wave velocity in Japan. The applicability of this method is validated by comparisons between the measured and estimated time-averaged shear wave velocity to depth Z( V SZ, 5< Z < 300 m). Using a second-order polynomial regression relating log V SZ and log V S30, the estimated V S30 values agree well with the measured values. We also find that V S30 is directly related with the ratio of radial to vertical components of the initial P-wave velocity time series ( R P). Compared with the theoretical method, the empirical relationship between R P and V S30 has an improvement in the accuracy for V S30 estimation, is basically region-independent for Japan and Central and Eastern North America (CENA), does not need any other parameters, and is potentially useful for other regions of the world.

scholarly journals Calibrating a new attenuation curve for the Dead Sea region using surface wave dispersion surveys in sites damaged by the 1927 Jericho earthquake

Solid Earth ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 379-390 ◽  
Author(s):  
Yaniv Darvasi ◽  
Amotz Agnon
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Dead Sea ◽  
Attenuation Curve ◽  
Surface Wave Dispersion ◽  
Near Surface ◽  
Moderate Seismicity ◽  
Local Point ◽  
The Dead

Abstract. Instrumental strong motion data are not common around the Dead Sea region. Therefore, calibrating a new attenuation equation is a considerable challenge. However, the Holy Land has a remarkable historical archive, attesting to numerous regional and local earthquakes. Combining the historical record with new seismic measurements will improve the regional equation. On 11 July 1927, a rupture, in the crust in proximity to the northern Dead Sea, generated a moderate 6.2 ML earthquake. Up to 500 people were killed, and extensive destruction was recorded, even as far as 150 km from the focus. We consider local near-surface properties, in particular, the shear-wave velocity, as an amplification factor. Where the shear-wave velocity is low, the seismic intensity far from the focus would likely be greater than expected from a standard attenuation curve. In this work, we used the multichannel analysis of surface waves (MASW) method to estimate seismic wave velocity at anomalous sites in Israel in order to calibrate a new attenuation equation for the Dead Sea region. Our new attenuation equation contains a term which quantifies only lithological effects, while factors such as building quality, foundation depth, topography, earthquake directivity, type of fault, etc. remain out of our scope. Nonetheless, about 60 % of the measured anomalous sites fit expectations; therefore, this new ground-motion prediction equation (GMPE) is statistically better than the old ones. From our local point of view, this is the first time that integration of the 1927 historical data and modern shear-wave velocity profile measurements improved the attenuation equation (sometimes referred to as the attenuation relation) for the Dead Sea region. In the wider context, regions of low-to-moderate seismicity should use macroseismic earthquake data, together with modern measurements, in order to better estimate the peak ground acceleration or the seismic intensities to be caused by future earthquakes. This integration will conceivably lead to a better mitigation of damage from future earthquakes and should improve maps of seismic hazard.

scholarly journals Empirical relationships of shear wave velocity, SPT-N value and vertical effective stress for different soils in Mashhad, Iran

2015 ◽  
Vol 58 (3) ◽  
Author(s):  
Azam Ghazi ◽  
Naser Hafezi Moghadas ◽  
Hosein Sadeghi ◽  
Mohamad Ghafoori ◽  
Gholam Reza Lashkaripur
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Effective Stress ◽  
Shear Wave Velocity ◽  
Response Analysis ◽  
Empirical Relationships ◽  
Data Set ◽  
Fine Grain ◽  
Geophysical Investigations ◽  
Vertical Effective Stress

<p>Shear wave velocity, V<sub>s</sub>, is one of the important input parameters in seismic response analysis of the ground. Various methods have been examined to measure the soil V<sub>s</sub> directly. Direct measurement of V<sub>s</sub> is time consuming and costly, therefore many researchers have been trying to update empirical relationships between V<sub>s</sub> and other geotechnical properties of soils such as SPT Blow count, SPT-N. In this study the existence of a statistical relationship between V<sub>s</sub>, SPT-N<sub>60 </sub>and vertical effective stress, signa<sub>nu</sub>´, is investigated. Data set we used in this study was gathered from geotechnical and geophysical investigations reports. The data have been extracted from more than 130 numbers of geotechnical boreholes from different parts of Mashhad city. In each borehole the V<sub>s</sub> has been measured by downhole method at two meter intervals. The SPT test also has performed at the same depth. Finally relationships were developed by regression analysis for gravels, sands and fine grain soils. The proposed relationships indicate that V<sub>s</sub> is strongly dependent on signa<sub>nu</sub>´. In this paper the effect of fine percent also is considered on the V<sub>s</sub> estimation.</p>

Influence of Seasonal Frozen Soil on Near‐Surface Shear Wave Velocity in Eastern Hokkaido, Japan

2019 ◽  
Vol 46 (16) ◽  
pp. 9497-9508 ◽  
Author(s):  
Y. Miao ◽  
Y. Shi ◽  
H. Y. Zhuang ◽  
S. Y. Wang ◽  
H. B. Liu ◽  
...  
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Frozen Soil ◽  
Surface Shear ◽  
Near Surface ◽  
Seasonal Frozen Soil ◽  
Surface Shear Wave

In Situ Shear-Wave Velocity Assessment at the Delaney Park Downhole Array, Anchorage, Alaska

2020 ◽  
Vol 91 (6) ◽  
pp. 3381-3390
Author(s):  
Hai-Yun Wang ◽  
Wei-Ping Jiang
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Great Influence ◽  
Standard Penetration Test ◽  
Weak Anisotropy ◽  
Near Surface ◽  
Motion Data ◽  
Downhole Array

Abstract The shear-wave velocity (VS) in soil is an important parameter to characterize dynamic soil properties. The Delaney Park downhole array was deployed in 2003 without measuring the shear- and compression-wave velocity (VS and VP) profiles. Thornley et al. (2019) measured the VS and VP profiles using the downhole method after the sensor was removed from the 61 m borehole with casing in the array. However, the waves propagating along the casing wall may have a great influence on the recognition of the first arrival of waves propagating in the soil. Using horizontal and vertical components of weak-motion data of eight local earthquakes recorded by the array, in situ VS and VP profiles were assessed by the seismic interferometry based on deconvolution, respectively. The results are as follows. The VS and VP profiles computed by this study and measured by Thornley et al. (2019) are in relatively good agreement at a depth of 10–45 m and at a depth of 30–45 m, respectively, and in very poor agreement at other depths. The average VS profiles computed by this study are more consistent with the derived VS from the standard penetration test data at the site with slower near-surface velocities relative to the downhole logging analysis. There are strong anisotropy in the strata below 45 m and weak anisotropy with various degrees at various depths in the strata above 45 m.

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