Surface Seismic Measurements of Near-Surface P- and S-Wave Seismic Velocities at Earthquake Recording Stations, Seattle, Washington

1999 ◽  
Vol 15 (3) ◽  
pp. 565-584 ◽  
Author(s):  
Robert A. Williams ◽  
William J. Stephenson ◽  
Arthur D. Frankel ◽  
Jack K. Odum
Keyword(s):  
Seismic Refraction ◽  
Ground Surface ◽  
Industrial Area ◽  
High Amplitude ◽  
Seismic Velocities ◽  
S Wave ◽  
Near Surface ◽  
Sedimentary Deposits ◽  
Reflection Data ◽  
Seismic Reflections

We measured P- and S-wave seismic velocities to about 40-m depth using seismic-refraction/reflection data on the ground surface at 13 sites in the Seattle, Washington, urban area, where portable digital seismographs recently recorded earthquakes. Sites with the lowest measured Vs correlate with highest ground motion amplification. These sites, such as at Harbor Island and in the Duwamish River industrial area (DRIA) south of the Kingdome, have an average Vs in the upper 30 m (V¯s30) of 150 to 170 m/s. These values of V¯s30 place these sites in soil profile type E (V¯s30 < 180 m/s). A “rock” site, located at Seward Park on Tertiary sedimentary deposits, has a V¯s30 of 433 m/s, which is soil type C (V¯s30: 360 to 760 m/s). The Seward Park site V¯s30 is about equal to, or up to 200 m/s slower than sites that were located on till or glacial outwash. High-amplitude P- and S-wave seismic reflections at several locations appear to correspond to strong resonances observed in earthquake spectra. An S-wave reflector at the Kingdome at about 17 to 22 m depth probably causes strong 2-Hz resonance that is observed in the earthquake data near the Kingdome.

Effects of near-surface waveguides on shallow high-resolution seismic refraction and reflection data

1996 ◽  
Vol 23 (5) ◽  
pp. 495-498 ◽  
Author(s):  
J. O. A. Robertsson ◽  
K. Holliger ◽  
A. G. Green ◽  
A. Pugin ◽  
R. De Iaco
Keyword(s):  
High Resolution ◽  
Seismic Refraction ◽  
Near Surface ◽  
Reflection Data

scholarly journals Estimation of Geodynamic Properties using Seismic Techniques at a Steel Rolling Factory, Northwestern Gulf of Suez, Egypt

2020 ◽  
Vol 8 (6) ◽  
pp. 1785-1794
Keyword(s):  
Wave Velocity ◽  
Seismic Waves ◽  
Seismic Refraction ◽  
Industrial Area ◽  
P Wave ◽  
Gulf Of Suez ◽  
S Wave ◽  
P Waves ◽  
Steel Rolling ◽  
P Wave Velocity

The objective of the current investigations is to estimate the dynamic geotechnical properties necessary for evaluating the conditions of the subsurface in order to make better decisions for economic and safe designs of the proposed structures at a Steel Rolling Factory, Ataqa Industrial Area, Northwestern Gulf of Suez, Egypt. To achieve this purpose, four seismic refraction profiles were conducted to measure the velocity of primary seismic waves (P-waves) and four profiles were conducted using Multichannel Analysis of Surface Waves (MASW) technique in the same locations of refraction profiles to measure the velocity of shear waves (S-waves). SeisImager/2D Software Package was used in the analysis of the measured data. Data processing and interpretation reflect that the subsurface section in the study area consists of two layers, the first layer is a thin surface layer ranges in thickness from 1 to 4 meters with P-wave velocity ranges from 924 m/s to 1247 m/s and S-wave velocity ranges from 530 m/s to 745 m/s. The second layer has a P-wave velocity ranges from 1277 m/s to 1573 m/s and the S-wave velocity ranges from 684 m/s to 853 m/s. Geotechnical parameters were calculated for both layers. Since elastic moduli such as Poisson’s ratio, shear modulus, Young’s modulus, and bulk’s modulus were calculated. Competence scales such as material index, stress ratio, concentration index, and density gradient were calculated also. In addition, the ultimate and allowable bearing capacities

Foundation Evaluation of a Repeater Installation Building using Electrical Resistivity Tomography and Seismic Refraction Tomography

2019 ◽  
Vol 24 (1) ◽  
pp. 27-38
Author(s):  
B. Butchibabu ◽  
Prosanta K. Khan ◽  
P.C. Jha
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Seismic Refraction ◽  
P Wave ◽  
S Wave ◽  
Resistivity Tomography ◽  
Near Surface ◽  
Refraction Tomography ◽  
Subsurface Layers ◽  
Geophysical Investigations

Geophysical investigations were carried out for evaluation of damage and to assess the possible causes for repeated occurrence of damage at one of the buildings constructed for oil pumping in the northern part of India. Electrical Resistivity Tomography (ERT) and Seismic Refraction Tomography (SRT) techniques were adopted for studying the subsurface of the area around the building with an objective of ascertaining the cause of damage. High resolution imaging was done using both the techniques in this investigation. ERT delineated the presence of low resistivity (2 ohm-m) water filled voids below the structures and mapped different subsurface layers such as sandy soil, clay and sandstone in the study area. SRT revealed P-wave velocity ( V P ) of the subsurface medium in the range of 400–3,400 m/s. Corresponding densities and S-wave velocities ( V S ) were determined based on Gardner's and Castagna's relationships. Subsequently, the V P , V S and the modulus values were used in estimating compressibility of soil and rock strata. Results showed near surface layers were characterized by high compressibility (26.673 × 10 −5 Pa −1 ), decreases with depth. This paper presents the details of the site, techniques used in the investigation and correlation of geophysical results with lithological information, and the subsequent analysis for understanding the distress in the subsurface of the study area.

Seismic mapping and modeling of near‐surface sediments in polar areas

Geophysics ◽  
2003 ◽  
Vol 68 (2) ◽  
pp. 566-573 ◽  
Author(s):  
Tor Arne Johansen ◽  
Per Digranes ◽  
Mark van Schaack ◽  
Ida Lønne
Keyword(s):  
Water Saturation ◽  
Geological Mapping ◽  
P Wave ◽  
Unconsolidated Sediments ◽  
Polar Regions ◽  
Seismic Velocities ◽  
S Wave ◽  
Delta Front ◽  
Near Surface ◽  
Water Saturated

A knowledge of permafrost conditions is important for planning the foundation of buildings and engineering activities at high latitudes and for geological mapping of sediment thicknesses and architecture. The freezing of sediments is known to greatly affect their seismic velocities. In polar regions the actual velocities of the upper sediments may therefore potentially reveal water saturation and extent of freezing. We apply various strategies for modeling seismic velocities and reflectivity properties of unconsolidated granular materials as a function of water saturation and freezing conditions. The modeling results are used to interpret a set of high‐resolution seismic data collected from a glaciomarine delta at Spitsbergen, the Norwegian Arctic, where the upper subsurface sediments are assumed to be in transition from unfrozen to frozen along a transect landward from the delta front. To our knowledge, this is the first attempt to study pore‐fluid freezing from such data. Our study indicates that the P‐ and S‐wave velocities may increase as much as 80–90% when fully, or almost fully, water‐saturated unconsolidated sediments freeze. Since a small amount of frozen water in the voids of a porous rock can lead to large velocity increases, the freezing of sediments reduces seismic resolution; thus, the optimum resolution is obtained at locations where the sediments appear unfrozen. The reflectivity from boundaries separating sediments of slightly different porosity may depend more strongly on the actual saturation rather than changes in granular characteristics. For fully water‐saturated sediments, the P‐wave reflectivity decreases sharply with freezing, while the reflectivity becomes less affected as the water saturation is lowered. Thus, a combination of velocity and reflectivity information may reveal saturation and freezing conditions.

Seismic Microzonation for Denizli Metropolitan Area, Turkey

2015 ◽  
Vol 802 ◽  
pp. 40-44
Author(s):  
Ali Aydin ◽  
Erdal Akyol ◽  
Mahmud Gungor ◽  
Nuray Soyatik ◽  
Suat Tasdelen
Keyword(s):  
Urban Areas ◽  
Seismic Refraction ◽  
Seismic Microzonation ◽  
Seismic Velocities ◽  
Two Dimensional ◽  
S Wave ◽  
City Center ◽  
Wave Velocities ◽  
Municipal Authority ◽  
Use Studies

This study presents microzonation of the Denizli city center, is about 225 km2. It is mainly rely on t seismic velocities of the tested soil. For seismic microzonation area of has been selected as the study area. Seismic refraction methods have been used to generate two-dimensional profiles at 310 locations. These p and s wave velocities are used to estimate boundaries of the velocities at every 2 and 5 m intervals up to a depth of 60 m. The results are satisfactory for urban planning and it can successfully be used in urban areas. The municipal authority may be considered to use the results for land use studies.

Seismological studies in a rock body at Chalk River, Ontario and their relation to fractures

1982 ◽  
Vol 19 (8) ◽  
pp. 1535-1547 ◽  
Author(s):  
C. Wright
Keyword(s):  
Wave Velocity ◽  
Test Site ◽  
P Wave ◽  
Seismic Velocities ◽  
S Wave ◽  
P Waves ◽  
Rock Body ◽  
Near Surface ◽  
Wave Velocities ◽  
P Wave Velocity

Seismological experiments have been undertaken at a test site near Chalk River, Ontario that consists of crystalline rocks covered by glacial sediments. Near-surface P and S wave velocity and amplitude variations have been measured along profiles less than 2 km in length. The P and S wave velocities were generally in the range 4.5–5.6 and 2.9–3.2 km/s, respectively. These results are consistent with propagation through fractured gneiss and monzonite, which form the bulk of the rock body. The P wave velocity falls below 5.0 km/s in a region where there is a major fault and in an area of high electrical conductivity; such velocity minima are therefore associated with fracture systems. For some paths, the P and 5 wave velocities were in the ranges 6.2–6.6 and 3.7–4.1 km/s, respectively, showing the presence of thin sheets of gabbro. Temporal changes in P travel times of up to 1.4% over a 12 h period were observed where the sediment cover was thickest. The cause may be changes in the water table. The absence of polarized SH arrivals from specially designed shear wave sources indicates the inhomogeneity of the test site. A Q value of 243 ± 53 for P waves was derived over one relatively homogeneous profile of about 600 m length. P wave velocity minima measured between depths of 25 and 250 m in a borehole correlate well with the distribution of fractures inferred from optical examination of borehole cores, laboratory measurements of seismic velocities, and tube wave studies.

Crustal seismic velocity and density structure of the Intermontane and Coast belts, southwestern Cordillera

1998 ◽  
Vol 35 (12) ◽  
pp. 1362-1379 ◽  
Author(s):  
George D Spence ◽  
Nancy A McLean
Keyword(s):  
Upper Mantle ◽  
Lower Crust ◽  
Seismic Velocity ◽  
Gravity Data ◽  
Seismic Refraction ◽  
High Density ◽  
Western Coast ◽  
Seismic Velocities ◽  
Crust And Upper Mantle ◽  
Reflection Data

Seismic refraction - wide-angle reflection data were recorded along a 450 km profile across the Intermontane, Coast, and Insular belts of the Canadian Cordillera. Crust and upper mantle structure was interpreted from traveltime inversion and forward-amplitude modelling, and the resultant seismic velocities were used to constrain modelling of the Bouguer gravity data along the profile. A high-velocity, high-density block in the upper 8 km of crust was interpreted as the subsurface extension of Harrison terrane; the Harrison fault at its eastern boundary may extend to at least 8 km depth and perhaps 20 km. Throughout the crust, both seismic velocities and densities are in general high beneath the Insular belt, low beneath the Coast and western Intermontane belts, and intermediate beneath the eastern Intermontane belt. However, densities are unusually low in the lower crust beneath the Coast belt (2800 kg/m3), relative to velocities (6.6-6.8 km/s). This indicates that Coast belt plutonic material is present throughout the crust; strong upper mantle reflectivity, previously interpreted on a Lithoprobe reflection line beneath the western Coast belt, may be high-density residue associated with the unusually low density plutonic material. Based on gravity data, Wrangellia must terminate sharply against the western edge of the Coast belt. In the lower crust, the lowest seismic velocities are found vertically beneath the surface trace of the Fraser fault, where velocities just above the Moho only reach 6.5 km/s, in contrast with 6.8 km/s beneath the western Coast belt and eastern Intermontane belt. This provides support for a subvertical geometry for the Fraser fault, perhaps with a broad zone of diffuse shearing in the lower crust. At this location, the Fraser fault does not appear to vertically offset the Moho, which is well-constrained at a uniform depth of km east of the Harrison fault.

scholarly journals Integrated Offshore Seismic Survey Using an Unmanned Wave Glider

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 297
Author(s):  
Snons Cheong ◽  
Young-Jun Kim ◽  
Jong-Hwa Chun ◽  
Jung-Ki Kim ◽  
Shin Huh
Keyword(s):  
Single Channel ◽  
Seismic Refraction ◽  
Seismic Source ◽  
Offshore Structures ◽  
Seismic Survey ◽  
Acoustic Basement ◽  
Sedimentary Deposits ◽  
Reflection Data ◽  
Autonomous Surface Vehicle ◽  
Wave Glider

An autonomous surface vehicle, known as a wave glider, was used to record refracted and reflected signals from a seismic source penetrating the shallow subsurface. An integrated survey system consisting of a wave gilder and a human-operated source vessel was deployed. These survey systems are used to acquire wide-offset seismic survey data from specific areas, such as offshore structures. The wave gliders can collect seismic refraction and reflection data, which can be used to estimate subsurface information, e.g., acoustic wave velocity and subsurface structure. We processed raw data collected by a receiver equipped with the wave glider and used the relationship between travel time and offset distance to calculate the velocities of shallow sedimentary deposits and the acoustic basement. The velocities of the sedimentary deposits and basement were estimated to be 1557 and 3507 m/s, respectively. We then overlaid the velocities on subsurface data measured using a single-channel streamer. Our results indicate that unmanned equipment can be used for ocean exploration to aid offshore energy development.

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