FIELD MEASUREMENT OF THE ELECTROSEISMIC RESPONSE

Geophysics ◽  
1975 ◽  
Vol 40 (2) ◽  
pp. 233-245 ◽  
Author(s):  
Leland Timothy Long ◽  
Wayne K. Rivers
Keyword(s):  
Coastal Plain ◽  
Layered Medium ◽  
Sedimentary Rocks ◽  
Taylor Series Expansion ◽  
Seismic Source ◽  
Body Waves ◽  
Seismic Excitation ◽  
Electrode Spacing ◽  
Rayleigh Surface Waves ◽  
Wenner Array

The electroseismic response is a change in apparent resistivity induced by seismic excitation. It can be measured under field conditions with a conventional Wenner array and an explosive seismic source. In coastal plain sedimentary rocks near Gordon, Georgia, a Wenner array with 9-m electrode spacing measured a change in voltage of 100 to 300 μv per mm/sec of 15 hz vertical particle velocity at the surface. The response correlates best with the Rayleigh surface waves and compressional body waves. By assuming a layered medium which is excited uniformly by a seismic disturbance, we can use a Taylor series expansion of the voltage expression for a Wenner array in terms of layer resistivities to obtain estimates of the perturbations of the resistivities in the layers.

An experimental study of source motion synthesis from first arrivals

1963 ◽  
Vol 53 (5) ◽  
pp. 955-963
Author(s):  
Henry N. Pollack
Keyword(s):  
Experimental Study ◽  
Source Function ◽  
Seismic Source ◽  
The Body ◽  
Body Waves ◽  
Fixed Position ◽  
Explosive Source ◽  
Simple Medium ◽  
Surface Ice ◽  
Source Motion

Abstract The motion near a seismic source is synthesized from experimentally obtained seismograms of non-dispersed body waves. The body waves were emitted from an explosive source submerged in a lake with a frozen surface. The seismograms were recorded at several distances by moving the source to a greater depth for each record, while the seismometer remained in a fixed position on the surface ice sheet. All syntheses of the waveform one meter from the source yield the impulsive nature of the source. Deviations between the synthesized one-meter record and the observed one-meter motion are thought to reflect primarily the changing character of the shot medium with depth from the ice. These results indicate that over the short propagation distances (about three wavelengths for the higher frequencies recorded) through the simple medium of this experiment, the observed waveforms and their associated spectra retain characteristics of the source function. The records also yield some information regarding the nature and structure of the elastic medium about the source.

VELOCITY ANISOTROPY MEASUREMENTS IN WELLS

Geophysics ◽  
1966 ◽  
Vol 31 (5) ◽  
pp. 900-916 ◽  
Author(s):  
D. M. Vander Stoep
Keyword(s):  
Seismic Waves ◽  
Layered Medium ◽  
Sedimentary Rocks ◽  
Transversely Isotropic ◽  
Anisotropy Factor ◽  
Propagation Time ◽  
Reflection Seismology ◽  
Simple Description ◽  
Velocity Anisotropy ◽  
The Difference

Sedimentary rocks are generally anisotropic to the propagation of seismic waves. Anisotropy can be defined as the difference between propagation time predicted by the simple theory of Snell’s Law and observed propagation time between two points in a layered medium that lie on a line oblique to the layers. This difference can be explained by the more complicated theory of wave propagation in transversely isotropic materials. In the zone about the vertical that is of interest in reflection seismology, the effect of anisotropy usually can be described geometrically by an anisotropy factor A. This simple description is not valid for propagation directions making large angles with the normal to the layers. The anisotropy factor as well as the vertical velocity can vary with depth. A method is given for determining the factor A as a function of depth from a continuous velocity log and a range of oblique shots into a well phone. The method is applied to two field examples. In one of the examples, it is shown by data obtained from the larger shooting distances that the simple A factor description is inadequate for higher angles of propagation direction.

scholarly journals Teleseismic source parameters and rupture characteristics of the 24 November 1987, Superstition Hills earthquake

1990 ◽  
Vol 80 (1) ◽  
pp. 43-56 ◽  
Author(s):  
Lorraine J. Hwang ◽  
Harold Magistrale ◽  
Hiroo Kanamori
Keyword(s):  
Source Parameters ◽  
Seismic Source ◽  
Point Sources ◽  
Body Waves ◽  
Rupture Velocity ◽  
Total Moment ◽  
Long Period ◽  
The North ◽  
The Difference ◽  
Northern Segment

Abstract Long-period body waves from the 24 November 1987, Superstition Hills earthquake are studied to determine the focal mechanism and spatial extent of the seismic source. The earthquake is a complex event consisting of two spatially distinct subevents with different focal mechanisms. Two consistent models of rupture are developed. For both models, the second subevent begins 8 sec after the initiation of the first subevent and the preferred centroid depth lies between 4 to 8 km. Model 1 consists of two point sources separated by 15 to 20 km along strike of the Superstition Hills fault. Model 2 consists of one point source and one line source with a rupture velocity of 2.5 km/sec with moment release distributed along strike of the focal plane at a distance of 10 to 22 km from the epicenter. These moment release patterns show that a significant amount of long-period energy is radiated from the southern segment of the fault. Total moment release for both models is approximately 8 × 1025 dyne-cm. Both models also suggest a change of dip from near vertical near the epicenter to steeply southwesterly dipping along the southern segment of the fault. The difference in rupture characteristics and fault dips seen teleseismically is also reflected in aftershock and afterslip data, and crustal structure underlying the two fault segments. The northern segment had more aftershocks and a smaller proportion of afterslip than the southern segment. The boundary between the two segments lies at a step in the basement that separates a deeper metasedimentary basement to the south from a shallower crystalline basement to the north.

scholarly journals Geoelectrical and Geotechnical Characterization of Different Types of Soil in Ede, Osun State, Nigeria

2021 ◽  
Vol 6 (2) ◽  
Author(s):  
Wilfred N. Igboama ◽  
Olaide S. Hammed ◽  
Maruf T. Aroyehun ◽  
Nicholas U. Ugwu
Keyword(s):  
Organic Soil ◽  
Electrode Spacing ◽  
Dry Density ◽  
Sieve Analysis ◽  
Maximum Dry Density ◽  
Geotechnical Investigations ◽  
Different Types ◽  
Geoelectrical Resistivity ◽  
Wenner Array

Geoelectrical and geotechnical investigations were carried out to characterize soils from different locations in Ede, Osun State, Nigeria for engineering purposes. Wenner electrode configuration technique was deployed in carrying out the geoelectrical survey of about 40m for each profile. The data analysis was approached by plotting the apparent conductivity against electrode spacing (s) and the result was interpreted.  The geoelectrical resistivity survey revealed locations 1 and 2 with resistivity values of 25.01-419.22ohm-m (conductivity 0.002 - 0.194 (ohm-m)-1and 5.5-1246.57 ohm-m (conductivity = 0.0002 - 0.001 (ohm-m)-1) respectively could be classified as clay. Sample 3 recorded a resistivity value of 1.00- 22,787.39 ohm-m (conductivity= 0.00004- 1.00 (ohm-m)-1) thus, was classified as silt/sand respectively. Soil  from the said different locations in Ede, Nigeria, were tested in the Laboratory for certain properties like Atterberg limits, specific gravities, sieve analysis, compaction test, etc and the results showed that samples 1, 2 and 3 have specific gravity values of 2.50, 2.13 and 2.40 respectively and could therefore be referred to as organic soil. Samples 1, 2 and 3 have maximum dry density (MDD) of 1.45g/cm3­, 1.92g/cm3, 1.95g/cm3 and optimum moisture content (OMC) of 15.40%, 13.36% and 9.61% respectively. The analysis conducted in this study revealed that the soil type found in Ede, Nigeria could be classified as silt-clay, sandy clay, clay and sand.Keywords- Electrical conductivity, Characterization, Compaction, Plasticity, Wenner array.

The January 4, 1989, Earthquake in Bluffton, South Carolina, and its Tectonic Implications

1991 ◽  
Vol 62 (2) ◽  
pp. 139-142
Author(s):  
P. Talwani ◽  
K. Rajendran
Keyword(s):  
South Carolina ◽  
Ground Motion ◽  
Coastal Plain ◽  
Seismic Source ◽  
Early Morning ◽  
Source Zone ◽  
The Past ◽  
Tectonic Implications ◽  
Lower South ◽  
Head Area

Abstract An earthquake of magnitude 2.8 occurred on January 4, 1989, at 9:39:01.47 UTC (4:39 am EST) near Bluffton, in the lower South Carolina Coastal Plain, a region of low seismicity. More than seventy people in the Bluffton-Hilton Head area reported either hearing or feeling this early morning event. Historically, there have been three earthquakes, two of which had a MMI ≥ V, near Savannah, 25 km southwest of this earthquake. Recent discoveries of earthquake induced liquefaction features in the Bluffton area suggested that this area had been subjected to large ground motion in the past. Together, these data lead to the preliminary inference of a possible seismic source zone near Bluffton.

Dynamic Topography Change of the Eastern United States Since 3 Million Years Ago

Science ◽  
2013 ◽  
Vol 340 (6140) ◽  
pp. 1560-1563 ◽  
Author(s):  
David B. Rowley ◽  
Alessandro M. Forte ◽  
Robert Moucha ◽  
Jerry X. Mitrovica ◽  
Nathan A. Simmons ◽  
...  
Keyword(s):  
Sea Level ◽  
Coastal Plain ◽  
Mantle Convection ◽  
Sedimentary Rocks ◽  
Ice Sheets ◽  
Glacial Isostatic Adjustment ◽  
Eastern United States ◽  
Dynamic Topography ◽  
Isostatic Adjustment ◽  
Global Sea Level

Sedimentary rocks from Virginia through Florida record marine flooding during the mid-Pliocene. Several wave-cut scarps that at the time of deposition would have been horizontal are now draped over a warped surface with a maximum variation of 60 meters. We modeled dynamic topography by using mantle convection simulations that predict the amplitude and broad spatial distribution of this distortion. The results imply that dynamic topography and, to a lesser extent, glacial isostatic adjustment account for the current architecture of the coastal plain and proximal shelf. This confounds attempts to use regional stratigraphic relations as references for longer-term sea-level determinations. Inferences of Pliocene global sea-level heights or stability of Antarctic ice sheets therefore cannot be deciphered in the absence of an appropriate mantle dynamic reference frame.

On the use of a seismic sensor as a seismic source

Geophysics ◽  
2013 ◽  
Vol 78 (5) ◽  
pp. A39-A43
Author(s):  
David F. Halliday ◽  
Taiwo Fawumi ◽  
Johan O. A. Robertsson ◽  
Ed Kragh
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Group Velocity ◽  
Seismic Source ◽  
Body Waves ◽  
Seismic Sources ◽  
Wave Group ◽  
Seismic Sensors ◽  
Voltage Signal ◽  
Seismic Wavefield

We investigated the use of seismic sensors as small seismic sources. A voltage signal is applied to a geophone that forces the mass within the geophone to move. The movement of the mass generates a seismic wavefield that was recorded with an array of geophones operating in the conventional sense. We observed higher-frequency (25 Hz and above) surface and body waves propagating from the geophone source at offsets of 10 s of meters. We further found that the surface waves emitted from geophone sources can be used to generate a surface-wave group velocity map. We discuss potential developments and future applications.

Sign in / Sign up

Export Citation Format

Share Document