Near-Surface Geophysical Profiling Near Former Location of K-NET Tsukidate Strong Motion Station in Miyagi Prefecture, Japan

During the 2011 Earthquake off the Pacific Coast of Tohoku, high acceleration records with a PGA of 2.7 G were reported at the K-NET Tsukidate station (MYG004), where a maximum seismic intensity of 7 on the Japan Meteorological Agency (JMA) scale was observed. However, no major damage to the wooden houses in the area surrounding the station was reported. The objectives of this study are to obtain a 2D shallow soil profile of the area around the Tsukidate strong motion station (MYG004) located on the top of a 5 m cliff, and also to provide basic material for a detailed understanding of the high accelerations during the earthquake. We conducted a seismic refraction survey west of the station, and we used a fullwaveform inversion of the acquired seismic data to retrieve a 2D shallow soil profile. The inverted 2D soil model underlines a clear lateral S-wave velocity variation in the surface layer, and comparisons to results of the microtremor measurements using an array and horizontal-to-vertical ratio conducted along the seismic survey line show significant similarities to the lateral velocity variation revealed by our 2D inversion. We also examined the effect of this lack of velocity homogeneity on the soil response, and we found that it could play an important role in amplifying the content of the high frequencies.

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Structural interpretation using refraction velocities from marine seismic surveys

Geophysics ◽

10.1190/1.1442026 ◽

1986 ◽

Vol 51 (1) ◽

pp. 12-19 ◽

Cited By ~ 3

Author(s):

James F. Mitchell ◽

Richard J. Bolander

Keyword(s):

Sedimentary Rock ◽

Seismic Energy ◽

Seismic Survey ◽

Subsurface Structure ◽

Seismic Reflection Data ◽

Near Surface ◽

Reflection Data ◽

Wide Range ◽

Streamer Length ◽

Set Up

Subsurface structure can be mapped using refraction information from marine multichannel seismic data. The method uses velocities and thicknesses of shallow sedimentary rock layers computed from refraction first arrivals recorded along the streamer. A two‐step exploration scheme is described which can be set up on a personal computer and used routinely in any office. It is straightforward and requires only a basic understanding of refraction principles. Two case histories from offshore Peru exploration demonstrate the scheme. The basic scheme is: step (1) shallow sedimentary rock velocities are computed and mapped over an area. Step (2) structure is interpreted from the contoured velocity patterns. Structural highs, for instance, exhibit relatively high velocities, “retained” by buried, compacted, sedimentary rocks that are uplifted to the near‐surface. This method requires that subsurface structure be relatively shallow because the refracted waves probe to depths of one hundred to over one thousand meters, depending upon the seismic energy source, streamer length, and the subsurface velocity distribution. With this one requirement met, we used the refraction method over a wide range of sedimentary rock velocities, water depths, and seismic survey types. The method is particularly valuable because it works well in areas with poor seismic reflection data.

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Elastic displacements in the near-field of a propagating fault

Bulletin of the Seismological Society of America ◽

10.1785/bssa0590020865 ◽

1969 ◽

Vol 59 (2) ◽

pp. 865-908

Author(s):

N. A. Haskell

Keyword(s):

Fault Plane ◽

Near Field ◽

Strong Motion ◽

Dislocation Motion ◽

Displacement Discontinuity ◽

Wave Form ◽

Strong Motion Station ◽

Ramp Function ◽

Wave Forms ◽

Parkfield Earthquake

abstract Displacement, particle velocity, and acceleration wave forms in the near field of a propagating fault have been computed by numerical integration of the Green's function integrals for an infinite medium. The displacement discontinuity (dislocation) on the fault plane is assumed to have the form of a unilaterally propagating finite ramp function in time. The calculated wave forms in the vicinity of the fault plane are quite similar to those observed at the strong motion station nearest the fault plane at the Parkfield earthquake. The comparison suggests that the propagating ramp time function is roughly representative of the main features of the dislocation motion on the fault plane, but that the actual motion has somewhat more high frequency complexity. Calculated amplitudes indicate that the average final dislocation on the fault at the Parkfield earthquake was more than an order of magnitude greater than the offsets observed on the visible surface trace. Computer generated wave form plots are presented for a variety of locations with respect to the fault plane and for two different assumptions on the relation between fault length and ramp function duration.

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ADAPTATION OF THE METHOD OF CHROMATOGRAPHIC ANALYSIS OF GASOLINE TO ACHIEVE PURPOSES OF GEOCHEMICAL PROSPECTING FOR OIL AND GAS

Oil and Gas Studies ◽

10.31660/0445-0108-2018-6-16-23 ◽

2019 ◽

pp. 16-23

Author(s):

A. R. Kurchikov ◽

R. I. Timshanov ◽

E. A. Ustimenko

Keyword(s):

Chromatographic Analysis ◽

Oil And Gas ◽

Seismic Survey ◽

Near Surface ◽

Petroleum Potential ◽

Geological Interpretation ◽

Gasoline Hydrocarbons ◽

Snow Water ◽

Individual Hydrocarbons ◽

Background Content

Geochemical survey is commonly applied during geological exploration to predict petroleum potential of large areas and to estimate the content of traps identified by the results of seismic survey. C1-C6 hydrocarbon concentrations in samples of surface and subsurface air, soil, snow, water, etc. are used as predictive indicators. At the exploration stage the capabilities of geochemical methods can be significantly expanded by comparing the content of gasoline hydrocarbons in samples of formation fluids and in samples of near-surface sediments. The method of chromatographic analysis of gasolines Chromatec Gazolin has been adapted for sample analysis. The taken measures to increase the sensitivity allowed us to register individual hydrocarbons C1-C10 in concentrations up to 0,01 ppb, which is obviously lower than their background content in the oil prospect areas. The revealed patterns are used in the geological interpretation of geochemical distributions based on theoretical ideas about the subvertical migration of hydrocarbons from the reservoir to the surface.

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What Is Fling Step? Its Theory, Simulation Method, and Applications to Strong Ground Motion near Surface Fault Ruptures

Bulletin of the Seismological Society of America ◽

10.1785/0120210046 ◽

2021 ◽

Author(s):

Yoshiaki Hisada ◽

Shinya Tanaka

Keyword(s):

Velocity Structure ◽

Seismic Velocity ◽

Strong Motion ◽

Theoretical Method ◽

Simulation Method ◽

Near Surface ◽

Seismic Velocity Structure ◽

Strong Motion Records ◽

Near Fault ◽

Fling Step

ABSTRACT We present the theory of the fling step and a theoretical method for simulating accurately the near-fault strong motions, and apply it to reproduce various strong-motion records near surface faults. Theoretically, the fling step is the contribution of the static Green’s function in the representation theorem (Hisada and Bielak, 2003), and we show that this theory holds for any seismic velocity structure. We first demonstrate the validity of this theory using theoretical solutions of a circular fault model in a homogeneous full-space. Next, we apply the theory to layered half-spaces, present a theoretical method based on the wavenumber integration method, and introduce various techniques to simulate the near-fault ground motions including fling steps with high accuracy. Finally, we demonstrate the effectiveness of the method by reproducing various strong-motion records near surface fault ruptures and discuss the characteristics of near-fault strong motions including the fling step and the forward directivity pulse. We made all of the software and data used in this article available on the internet.

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Shallow velocity structure and poisson's ratio at the Tarzana, California, strong-motion accelerometer site

Bulletin of the Seismological Society of America ◽

10.1785/bssa0860061704 ◽

1996 ◽

Vol 86 (6) ◽

pp. 1704-1713 ◽

Cited By ~ 2

Author(s):

R. D. Catchings ◽

W. H. K. Lee

Keyword(s):

Urban Areas ◽

Velocity Structure ◽

Strong Motion ◽

P Wave ◽

S Wave ◽

Near Surface ◽

Velocity Models ◽

Wave Velocities ◽

Poisson's Ratios ◽

Poisson’S Ratios

Abstract The 17 January 1994, Northridge, California, earthquake produced strong ground shaking at the Cedar Hills Nursery (referred to here as the Tarzana site) within the city of Tarzana, California, approximately 6 km from the epicenter of the mainshock. Although the Tarzana site is on a hill and is a rock site, accelerations of approximately 1.78 g horizontally and 1.2 g vertically at the Tarzana site are among the highest ever instrumentally recorded for an earthquake. To investigate possible site effects at the Tarzana site, we used explosive-source seismic refraction data to determine the shallow (<70 m) P-and S-wave velocity structure. Our seismic velocity models for the Tarzana site indicate that the local velocity structure may have contributed significantly to the observed shaking. P-wave velocities range from 0.9 to 1.65 km/sec, and S-wave velocities range from 0.20 and 0.6 km/sec for the upper 70 m. We also found evidence for a local S-wave low-velocity zone (LVZ) beneath the top of the hill. The LVZ underlies a CDMG strong-motion recording site at depths between 25 and 60 m below ground surface (BGS). Our velocity model is consistent with the near-surface (<30 m) P- and S-wave velocities and Poisson's ratios measured in a nearby (<30 m) borehole. High Poisson's ratios (0.477 to 0.494) and S-wave attenuation within the LVZ suggest that the LVZ may be composed of highly saturated shales of the Modelo Formation. Because the lateral dimensions of the LVZ approximately correspond to the areas of strongest shaking, we suggest that the highly saturated zone may have contributed to localized strong shaking. Rock sites are generally considered to be ideal locations for site response in urban areas; however, localized, highly saturated rock sites may be a hazard in urban areas that requires further investigation.

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Near-surface glaciotectonic structures in the sediments of an overdeepened glacial valley revealed by a shallow 3D seismic survey

10.5194/egusphere-egu21-8195 ◽

2021 ◽

Author(s):

David Tanner ◽

Hermann Buness ◽

Thomas Burschil

Keyword(s):

Seismic Reflection ◽

P Wave ◽

Seismic Survey ◽

Small Scale ◽

Academic Press ◽

Near Surface ◽

Glacial Sediments ◽

Area Source ◽

Terminal Moraine ◽

Rhine Valley

Glaciotectonic structures commonly include thrusting and folding, often as multiphase deformation. Here we present the results of a small-scale 3-D P-wave seismic reflection survey of glacial sediments within an overdeepened glacial valley in which we recognise unusual folding structures in front of push-moraine. The study area is in the Tannwald Basin, in southern Germany, about 50 km north of Lake Constance, where the basin is part of the glacial overdeepened Rhine Valley. The basin was excavated out of Tertiary Molasse sediments during the Hosskirchian stage, and infilled by 200 m of Hosskirchian and Rissian glacioclastics (Dietmanns Fm.). After an unconformity in the Rissian, a ca. 7 m-thick till (matrix-supported diamicton) was deposited, followed by up to 30 m of Rissian/W&#252;rmian coarse gravels and minor diamictons (Illmensee Fm.). The terminal moraine of the last W&#252;rmian glaciation overlies these deposits to the SW, not 200 m away.We conducted a 3-D, 120 x 120 m&#178;, P-wave seismic reflection survey around a prospective borehole site in the study area. Source/receiver points and lines were spaced at 3 m and 9 m, respectively. A 10 s sweep of 20-200 Hz was excited by a small electrodynamic, wheelbarrow-borne vibrator twice at every of the 1004 realized shot positions. We recognised that the top layer of coarse gravel above the till is folded, but not in the conventional buckling sense, rather as cuspate-lobate folding. The fold axes are parallel to the terminal moraine front. The wavelength of the folding varies between 40 and 80 m, and the thickness of the folded layer is on average about 20 m. Cuspate-lobate folding is typical for deformation of layers of differing mechanical competence (after Ramsay and Huber 1987; &#181;1/&#181;2 less than 10), so this tell us something about the relative competence (or stiffness) of the till layer compared to the coarse clastics above. We also detected small thrust faults that are also parallel to the push-moraine, but these have very little offset and most of the deformation was achieved by folding.Ramsay, J.G. and Huber, M. I. (1987): The techniques of modern structural geology, vol. 2: Folds and fractures: Academic Press, London, 700 pp.

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Estimation of the Rupture History of the 2008 Mw8.0 Wenchuan Earthquake by Joint Inversion of Teleseismic and Strong-Motion Records

Advances in Civil Engineering ◽

10.1155/2020/8810218 ◽

2020 ◽

Vol 2020 ◽

pp. 1-13

Author(s):

Deyu Yin ◽

Yun Dong ◽

Qifang Liu ◽

Yuexin She ◽

Jingke Wu ◽

...

Keyword(s):

Wenchuan Earthquake ◽

Strong Motion ◽

Inversion Method ◽

Near Surface ◽

Strong Motion Records ◽

The Wenchuan Earthquake ◽

Finite Fault ◽

History Of ◽

Beichuan Fault ◽

Dip Angle

In order to reproduce the rupture history of the 2008 Mw8.0 Wenchuan earthquake, the teleseismic and strong-motion records are adopted. Based on a multiple-segment, variable-slip model, the finite fault inversion method is utilized to recover the rupture process. The results are as follows: (1) the rupture duration of the Wenchuan earthquake is about 100 s, and the released seismic moment is 1.24 × 1021 N·m, equal to the moment magnitude Mw8.0. There are 5 asperities on the fault plane, indicating that the earthquake is composed of at least 5 subevents. (2) The slip is mainly distributed on the Beichuan fault, indicating that the Beichuan fault is the main rupture fault. On the southern part of the Beichuan fault, the dislocation underside the Longmenshan area and Hongkou-Yingxiu near-surface area is dominated by thrust, and the maximum slip is 11.8 m. Slip between the Yuejiashan and Qingping area is dominated by thrust. On the northern part of the Beichuan fault, the area under Beichuan is dominated by thrust, the slip under Nanba is thrust and strike, near Qingchuan, the slip turns into the strike slip, and the maximum slip is 13.1 m. The dislocation under Bailu is also dominated by thrust, with maximum slip 8.9 m. (3) The rupture of the Wenchuan earthquake is mainly a unilateral rupture to the northeast. The rupture started at the low dip angle part of the Beichuan fault, and after 3 s, it propagated to the Pengguan fault. After 10 s, the largest asperity under Longmenshan in the south section of the Beichuan fault began to break, lasting for about 24 s. Then, the Xiaoyudong fault was triggered by the Pengguan fault, and the bilateral rupture of the high dip angle part of the Beichuan fault started at about 6 s. South section of the Beichuan fault began to break at about 35 s, and at 43 s, 63 s, and 80 s, the rupture extended to Beichuan, Nanba, and Qingchuan areas.

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Bromide redistribution as influenced by landscape morphology and pedogenic properties in a variable glacial till landscape: A quantitative examination

Canadian Journal of Soil Science ◽

10.4141/cjss07073 ◽

2008 ◽

Vol 88 (4) ◽

pp. 491-499 ◽

Cited By ~ 4

Author(s):

P R Bullock ◽

D A Whetter ◽

L G Fuller

Keyword(s):

Soil Properties ◽

Soil Profile ◽

Digital Terrain Model ◽

Glacial Till ◽

Spatial And Temporal Variability ◽

Predictive Tool ◽

Near Surface ◽

Surface Flows ◽

Digital Terrain ◽

Profile Development

The spatial and temporal variability of soil properties with depth in the profile and across landscape positions results in diverse patterns of water and solute distribution over the landscape. Vertical and lateral movement of soluble nutrients within the soil profile influences the availability of nutrients required for crop growth, and the entry of nutrients into groundwater and surface water systems. However, commonly used geomorphic concepts such as crest and depression are not rigorously, quantitatively defined. The objective of this study was to determine the influence of quantitative topographic variables and zones of relative surface flows on vertical and lateral redistribution of a bromide tracer under field conditions in a variable glacial till landscape under zero tillage agricultural management. Tracer plots were established on three representative soil-slope associations and digital terrain models (DTM) were produced for determining slope gradient (G), horizontal curvature (Kh), vertical curvature (Kv), mean curvature (H) and accumulation curvature (Ka). Models of accumulation, transit and dissipation (ATD) zones of surface flows were produced for each digital elevation model (DEM) using data on mean and accumulation curvatures. Topographic variables and soil properties had mixed ability to predict bromide redistribution parameters. Soil profile development indicators were negatively correlated with bromide recovery, indicating that increased profile development resulted in more redistribution and lower recovery rates. Pedogenic indicators were significantly different between ATD zones, with depth to calcium carbonate, A horizon thickness, solum thickness and profile development indicator all significantly greater at accumulation zones relative to dissipation or transit zones, indicating that profile development was greatest at accumulation zones. However, the concept of ATD zones did not correlate significantly with bromide redistribution parameters. The utility of ATD zones as a predictive tool for static soil properties is limited by differing hydrologic regime and pedogenic processes occurring at lower slope positions, as a result of near-surface, dynamic water tables. Previous research, however, has shown that topographic variables and concepts of landscape element complexes have some utility in determining spatial variability of deep solute percolation and determination of potential for groundwater impacts. This study indicates that increased N application in convergent portions of the landscape may result in higher rates of deep percolation and removal of N from the crop rooting zone, in areas of depression-focused recharge, when environmental conditions are favourable for such. Key words: Solute redistribution, bromide tracer, digital terrain model, topography, landscape

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