Effect of cable capacitance on in‐situ borehole geophone calibration

Geophysics ◽  
1998 ◽  
Vol 63 (1) ◽  
pp. 18-24 ◽  
Author(s):  
Hsi‐Ping Liu ◽  
Richard E. Warrick
Keyword(s):  
Wave Propagation ◽  
San Francisco ◽  
Ground Motions ◽  
Vertical Component ◽  
Step Test ◽  
Deep Borehole ◽  
Earthquake Hazards ◽  
Ferro Magnet ◽  
Phase Ellipse

Using 2-Hz electromagnetic moving‐coil geophones as sensing elements, we have constructed and deployed three‐component seismometers in boreholes at various sites for wave‐propagation studies associated with earthquake hazards (Liu et al., 1991). For example, one such seismometer has been deployed in a 88-m deep borehole reaching bedrock in the Marina District of San Francisco since 1990 (Liu et al., 1992) for the purpose of comparing ground motions in the bedrock and those at the surface. Periodic calibrations for such geophones are necessary to check if the geophone parameters have changed because of decreased magnetization of the geophone ferro‐magnet. For example, the coil transductance of the vertical‐component geophone of the borehole seismometer mentioned above was calibrated to be 121 V-s/m using phase‐ellipse test and step test before deployment. Sixty six months after the deployment, the coil transductance, when calibrated in situ and with a 100-m intervening cable between the geophone and the calibration instrument, was found to be 114 V-s/m.

On the characteristics of local geology and their influence on ground motions generated by the Loma Prieta earthquake in the San Francisco Bay region, California

1992 ◽  
Vol 82 (2) ◽  
pp. 603-641 ◽  
Author(s):  
Roger D. Borcherdt ◽  
Gary Glassmoyer
Keyword(s):  
Ground Motion ◽  
San Francisco ◽  
San Francisco Bay ◽  
Ground Motions ◽  
Loma Prieta Earthquake ◽  
Franciscan Complex ◽  
Horizontal Acceleration ◽  
Geological Conditions ◽  
Peak Horizontal Acceleration ◽  
Loma Prieta

Abstract Strong ground motions recorded at 34 sites in the San Francisco Bay region from the Loma Prieta earthquake show marked variations in characteristics dependent on crustal structure and local geological conditions. Peak horizontal acceleration and velocity inferred for sites underlain by “rock” generally occur on the transverse component of motion. They are consistently greater with lower attenuation rates than the corresponding mean value predicted by empirical curves based on previous strong-motion data. Theoretical amplitude distributions and synthetic seismograms calculated for 10-layer models suggest that “bedrock” motions were elevated due in part to the wide-angle reflection of S energy from the base of a relatively thin (25 km) continental crust in the region. Characteristics of geologic and geotechnical units as currently mapped for the San Francisco Bay region show that average ratios of peak horizontal acceleration, velocity and displacement increase with decreasing mean shear-wave velocity. Ratios of peak acceleration for sites on “soil” (alluvium, fill/Bay mud) are statistically larger than those for sites on “hard rock” (sandstone, shale, Franciscan Complex). Spectral ratios establish the existence of predominant site periods with peak amplifications near 15 for potentially damaging levels of ground motion at some sites underlain by alluvium and fill/bay mud. Average spectral amplifications inferred for vertical and the mean horizontal motion are, respectively, (1,1) for sites on the Franciscan Complex (KJf), (1.4, 1.5) for sites on Mesozoic and Tertiary rocks (TMzs), (2.1, 2.0) for sites on the Santa Clara Formation (QTs), (2.3, 2.9) for sites on alluvium (Qal), and (2.1, 4.0) for sites on fill/Bay mud (Qaf/Qhbm). These mean values are not statistically different at the 5% significance level from those inferred from previous low-strain data. Analyses suggest that soil amplification and reflected crustal shear energy were major contributors to levels of ground motion sufficient to cause damage to vulnerable structures at distances near 100 km in the cities of San Francisco and Oakland.

Conditioned Simulation of Ground-Motion Time Series at Uninstrumented Sites Using Gaussian Process Regression

2021 ◽  
Author(s):  
Aidin Tamhidi ◽  
Nicolas Kuehn ◽  
S. Farid Ghahari ◽  
Arthur J. Rodgers ◽  
Monica D. Kohler ◽  
...  
Keyword(s):  
Time Series ◽  
Gaussian Process ◽  
Ground Motion ◽  
San Francisco ◽  
Earthquake Engineering ◽  
Seismic Analysis ◽  
Ground Motions ◽  
Free Field ◽  
Gaussian Process Regression ◽  
Motion Time

ABSTRACT Ground-motion time series are essential input data in seismic analysis and performance assessment of the built environment. Because instruments to record free-field ground motions are generally sparse, methods are needed to estimate motions at locations with no available ground-motion recording instrumentation. In this study, given a set of observed motions, ground-motion time series at target sites are constructed using a Gaussian process regression (GPR) approach, which treats the real and imaginary parts of the Fourier spectrum as random Gaussian variables. Model training, verification, and applicability studies are carried out using the physics-based simulated ground motions of the 1906 Mw 7.9 San Francisco earthquake and Mw 7.0 Hayward fault scenario earthquake in northern California. The method’s performance is further evaluated using the 2019 Mw 7.1 Ridgecrest earthquake ground motions recorded by the Community Seismic Network stations located in southern California. These evaluations indicate that the trained GPR model is able to adequately estimate the ground-motion time series for frequency ranges that are pertinent for most earthquake engineering applications. The trained GPR model exhibits proper performance in predicting the long-period content of the ground motions as well as directivity pulses.

scholarly journals Ground motion prediction from nearest seismogenic zones in and around Greater Cairo Area, Egypt

2010 ◽  
Vol 10 (7) ◽  
pp. 1495-1511 ◽  
Author(s):  
Keyword(s):  
Ambient Noise ◽  
Ground Motions ◽  
Empirical Relationship ◽  
Seismic Events ◽  
Ground Motion Prediction ◽  
Source Characterization ◽  
Source Characteristics ◽  
Rupture Length ◽  
Greater Cairo

Abstract. This paper reviews the likely source characteristics, focal source mechanism and fault patterns of the nearest effective seismogenic zones to Greater Cairo Area. Furthermore, Mmax and ground accelerations related to the effective seismic events expected in future from those seismogenic zones are well evaluated. For this purpose, the digital waveform of earthquakes than ML=3 that occurred in and around Greater Cairo Area from 1997 to 2008 which have been recorded by the Egyptian National Seismological Network, are used to study source characterization, focal mechanism and fault pattern of the seismogenic zones around Greater Cairo Area. The ground motions are predicted from seismogenic zones to assess seismic hazard in the northeastern part of Greater Cairo, where three effective seismogenic zones, namely Abou Zabul, southeast Cairo trend and Dahshour area, have the largest effect to the Greater Cairo Area. The Mmax was determined, based upon an empirical relationship between the seismic moment and the rupture length of the fault during the earthquake. The estimated Mmax expected from Abou Zabul, southeast Cairo trend, Dahshour seismic sources are of Mw magnitudes equal to 5.4, 5.1, and 6.5, respectively. The predominant fundamental frequency and soil amplification characteristics at the area were obtained using boreholes data and in-situ ambient noise measurement.

Effects of local geological conditions in the San Francisco Bay region on ground motions and the intensities of the 1906 earthquake

1976 ◽  
Vol 66 (2) ◽  
pp. 467-500 ◽  
Author(s):  
Roger D. Borcherdt ◽  
James F. Gibbs
Keyword(s):  
San Francisco ◽  
San Francisco Bay ◽  
Ground Motions ◽  
Empirical Relation ◽  
Good Evidence ◽  
Average Intensity ◽  
Seismic Zonation ◽  
Nuclear Explosions ◽  
Geological Conditions ◽  
Geological Units

abstract Measurements of ground motion generated by nuclear explosions in Nevada have been completed for 99 locations in the San Francisco Bay region, California. The recordings show marked amplitude variations in the frequency band 0.25 to 3.0 Hz that are consistently related to the local geological conditions of the recording site. The average spectral amplifications observed for vertical and horizontal ground motions are, respectively: (1, 1) for granite, (1.5, 1.6) for the Franciscan Formation, (3.0, 2.7) for the Santa Clara Formation, (3.3, 4.4) for alluvium, and (3.7, 11.3) for bay mud. Spectral amplification curves define predominant ground frequencies in the band 0.25 to 3.0 E for bay mud sites and for some alluvial sites. Amplitude spectra computed from recordings of seismic background noise at 50 sites do not generally define predominant ground frequencies. The intensities ascribed to various sites in the San Francisco Bay region for the California earthquake of April 18, 1906, are strongly dependent on distance from the zone of surface faulting and the geological character of the ground. Considering only those sites (approximately one square city block in size) for which there is good evidence for the degree of ascribed intensity, the intensities for 917 sites on Franciscan rocks generally decrease with the logarithm of distance as Intensity = 2 . 6 9 - 1 . 9 0 log ( Distance in kilometers ) . ( 1 ) For sites on other geological units, intensity increments, derived from this empirical relation, correlate strongly with the Average Horizontal Spectral Amplifications (AHSA) according to the empirical relation Intensity Increment = 0 . 2 7 + 2 . 7 0 log ( AHSA ) . ( 2 ) Average intensity increments predicted for the various geological units are −0.3 for granite, 0.2 for the Franciscan Formation, 0.6 for the Great Valley sequence, 0.8 for the Santa Clara Formation, 1.3 for alluvium, and 2.4 for bay mud. The maximum intensity map predicted on the basis of these data delineates areas in the San Francisco Bay region of potentially high intensity for large earthquakes on either the San Andreas fault or the Hayward fault. The map provides a crude form of seismic zonation for the region and may be useful for certain general types of land-use zonation.

Myogenic regulation of propagation in gastric smooth muscle

1985 ◽  
Vol 248 (5) ◽  
pp. G512-G520 ◽  
Author(s):  
N. G. Publicover ◽  
K. M. Sanders
Keyword(s):  
Wave Propagation ◽  
Conduction Velocity ◽  
Circular Muscle ◽  
Slow Waves ◽  
Gastric Distension ◽  
Gastric Smooth Muscle ◽  
Conduction Velocities ◽  
Axis Parallel ◽  
Myogenic Regulation

Experiments were performed to test the effects of frequency and stretch on the velocity of slow wave propagation parallel and perpendicular to the long axis of circular muscle fibers in the canine gastric antrum. Slow waves were evoked from one corner of a rectangular sheet of muscle and propagated throughout the tissue. Mathematics were derived and are presented, which simultaneously compute conduction velocities in each direction, regardless of electrode positions. Increased rate of stimulation had no significant effect on conduction velocity in the circumferential axis, but propagation slowed in the axis perpendicular to the circular fibers by an average of 25% over interstimulus intervals between 12 and 60 s. Conduction velocity was also a function of the degree of stretch. The most rapid conduction velocity occurred when muscles were stretched to an average of 118% of the resting, fasted length found in situ in the axis parallel to the circular fibers and 140% in the axis perpendicular to the circular fibers. Propagation was blocked by stretching muscles past 200% of resting length. These results suggest that the frequency of slow waves and gastric distension are intrinsic mechanisms capable of regulating the spread of slow waves.

scholarly journals Rossby Wave Propagation from the Arctic into the Midlatitudes: Does It Arise from In Situ Latent Heating or a Trans-Arctic Wave Train?

2020 ◽  
Vol 33 (9) ◽  
pp. 3619-3633 ◽  
Author(s):  
Tingting Gong ◽  
Steven B. Feldstein ◽  
Sukyoung Lee
Keyword(s):  
Wave Propagation ◽  
Rossby Wave ◽  
Wave Train ◽  
The Arctic ◽  
Latent Heating ◽  
Latent Heat Release ◽  
Rossby Wave Propagation ◽  
Rossby Wave Train ◽  
In Situ Generation

AbstractThe relationship between latent heating over the Greenland, Barents, and Kara Seas (GBKS hereafter) and Rossby wave propagation between the Arctic and midlatitudes is investigated using global reanalysis data. Latent heating is the focus because it is the most likely source of Rossby wave activity over the Arctic Ocean. Given that the Rossby wave time scale is on the order of several days, the analysis is carried out using a daily latent heating index that resembles the interdecadal latent heating trend during the winter season. The results from regression calculations find a trans-Arctic Rossby wave train that propagates from the subtropics, through the midlatitudes, into the Arctic, and then back into midlatitudes over a period of about 10 days. Upon entering the GBKS, this wave train transports moisture into the region, resulting in anomalous latent heat release. At high latitudes, the overlapping of a negative latent heating anomaly with an anomalous high is consistent with anomalous latent heat release fueling the Rossby wave train before it propagates back into the midlatitudes. This implies that the Rossby wave propagation from the Arctic into the midlatitudes arises from trans-Arctic wave propagation rather than from in situ generation. The method used indicates the variance of the trans-Arctic wave train, but not in situ generation, and implies that the variance of the former is greater than that of latter. Furthermore, GBKS sea ice concentration regression against the latent heating index shows the largest negative value six days afterward, indicating that sea ice loss contributes little to the latent heating.

scholarly journals Simulation of the effect of stress-induced anisotropy on borehole compressional wave propagation

Geophysics ◽  
2014 ◽  
Vol 79 (4) ◽  
pp. D205-D216 ◽  
Author(s):  
Xinding Fang ◽  
Michael C. Fehler ◽  
Arthur Cheng
Keyword(s):  
Wave Propagation ◽  
Stress Concentration ◽  
Elastic Properties ◽  
Wave Velocity ◽  
Wave Amplitude ◽  
P Wave ◽  
Azimuthal Variation ◽  
P Wave Velocity ◽  
Velocity Region

Formation elastic properties near a borehole may be altered from their original state due to the stress concentration around the borehole. This can lead to an incorrect estimation of formation elastic properties measured from sonic logs. Previous work has focused on estimating the elastic properties of the formation surrounding a borehole under anisotropic stress loading. We studied the effect of borehole stress concentration on sonic logging in a moderately consolidated Berea sandstone using a two-step approach. First, we used an iterative approach, which combines a rock-physics model and a finite-element method, to calculate the stress-dependent elastic properties of the rock around a borehole subjected to an anisotropic stress loading. Second, we used the anisotropic elastic model obtained from the first step and a finite-difference method to simulate the acoustic response of the borehole. Although we neglected the effects of rock failure and stress-induced crack opening, our modeling results provided important insights into the characteristics of borehole P-wave propagation when anisotropic in situ stresses are present. Our simulation results were consistent with the published laboratory measurements, which indicate that azimuthal variation of the P-wave velocity around a borehole subjected to uniaxial loading is not a simple cosine function. However, on field scale, the azimuthal variation in P-wave velocity might not be apparent at conventional logging frequencies. We found that the low-velocity region along the wellbore acts as an acoustic focusing zone that substantially enhances the P-wave amplitude, whereas the high-velocity region caused by the stress concentration near the borehole results in a significantly reduced P-wave amplitude. This results in strong azimuthal variation of P-wave amplitude, which may be used to infer the in situ stress state.

In situ measurements of compressional and shear wave propagation in marine sediments and comparison to geoacoustic models

2018 ◽  
Vol 144 (3) ◽  
pp. 1960-1960
Author(s):  
Kevin M. Lee ◽  
Megan S. Ballard ◽  
Andrew R. McNeese ◽  
Gabriel R. Venegas ◽  
Preston S. Wilson
Keyword(s):  
Wave Propagation ◽  
Shear Wave ◽  
Marine Sediments ◽  
In Situ Measurements

Modeling nonlinear site effects in physics-based ground motion simulations of the 2010–2011 Canterbury earthquake sequence

2020 ◽  
Vol 36 (2) ◽  
pp. 856-879 ◽  
Author(s):  
Christopher A de la Torre ◽  
Brendon A Bradley ◽  
Robin L Lee
Keyword(s):  
Wave Propagation ◽  
Ground Motion ◽  
Site Effects ◽  
Ground Motions ◽  
Site Amplification ◽  
Earthquake Sequence ◽  
Response Analysis ◽  
Site Specific ◽  
Ground Motion Simulations ◽  
Empirical Ground

This study examines the performance of nonlinear total stress one-dimensional (1D) wave propagation site response analysis for modeling site effects in physics-based ground motion simulations of the 2010–2011 Canterbury, New Zealand earthquake sequence. This approach explicitly models three-dimensional (3D) ground motion phenomena at the regional scale, and detailed site effects at the local scale. The approach is compared with a more commonly used empirical VS30-based method of computing site amplification for simulated ground motions, as well as prediction via an empirical ground motion model. Site-specific ground response analysis is performed at 20 strong motion stations in Christchurch for 11 earthquakes with 4.7≤ MW≤7.1. When compared with the VS30-based approach, the wave propagation analysis reduces both overall model bias and uncertainty in site-to-site residuals at the fundamental period, and significantly reduces systematic residuals for soft or “atypical” sites that exhibit strong site amplification. The comparable performance in ground motion prediction between the physics-based simulation method and empirical ground motion models suggests the former is a viable approach for generating site-specific ground motions for geotechnical and structural response history analyses.

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