Estimation of Ground Motions in the Valley of Mexico from Normal-Faulting, Intermediate-Depth Earthquakes in the Subducted Cocos Plate

1995 ◽  
Vol 11 (2) ◽  
pp. 233-247 ◽  
Author(s):  
Javier F. Pacheco ◽  
Shri Krishna Singh
Keyword(s):  
Seismic Waves ◽  
Ground Motions ◽  
Seismic Source ◽  
Source Model ◽  
Normal Faulting ◽  
Cocos Plate ◽  
Intermediate Depth ◽  
S Waves ◽  
Local Site ◽  
Seismic Source Model

The Valley of Mexico is exposed to seismic risk from normal-faulting, large intermediate-depth earthquakes. We explore two approaches to estimate future ground motions from such events at CU, a hill-zone site in the valley. In the first we obtain parameters of an ω2 seismic source model and determine amplification of seismic waves due to local site effects at CU. This permits estimation of Fourier spectrum of expected ground motion at CU from postulated earthquakes. We find that the S-waves suffer an amplification of 2.5 between 0.2 to 3.0 Hz. This amplification is similar to that observed from deep teleseismic events but differs from that obtained from shallow coastal events. In the second approach the available recordings at CU are used as empirical Green's functions (EGF) to synthesize motions from future large earthquakes. This approach is very powerful if the smaller event is truly an empirical Green's function for the postulated earthquake.

scholarly journals Model for Calculating Seismic Wave Spectrum Excited by Explosive Source

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Qian Xu ◽  
Zhong-Qi Wang
Keyword(s):  
Seismic Wave ◽  
Seismic Waves ◽  
Wave Spectrum ◽  
Seismic Source ◽  
Source Model ◽  
Detonation Pressure ◽  
Adiabatic Expansion ◽  
Main Frequency ◽  
Explosive Source ◽  
Seismic Source Model

To reveal the characteristics and laws of the seismic wavefield amplitude-frequency excited by explosive source, the method for computing the seismic wave spectrum excited by explosive was studied in this paper. The model for calculating the seismic wave spectrum excited by explosive source was acquired by taking the seismic source model of spherical cavity as the basis. The results of using this model show that the main frequency and the bandwidth of the seismic waves caused by the explosion are influenced by the initial detonation pressure, the adiabatic expansion of the explosive, and the geotechnical parameters, which increase with the reduction of initial detonation pressure and the increase of the adiabatic expansion. The main frequency and the bandwidth of the seismic waves formed by the detonation of the explosives in the silt clay increase by 23.2% and 13.6% compared to those exploded in the silt. The research shows that the theoretical model built up in this study can describe the characteristics of the seismic wave spectrum excited by explosive in a comparatively accurate way.

Primary ground displacements and seismic energy near the gnome explosion

1964 ◽  
Vol 54 (4) ◽  
pp. 1115-1126
Author(s):  
Joseph W. Berg ◽  
Lynn D. Trembly ◽  
Philip R. Laun
Keyword(s):  
Seismic Waves ◽  
Seismic Energy ◽  
Seismic Source ◽  
Detailed Comparison ◽  
Source Model ◽  
Half Cycle ◽  
Ground Displacement ◽  
Seismic Source Model ◽  
Displacement Wave ◽  
Spherical Divergence

Abstract Near-source measurements of seismic waves from gnome have been compared with a theoretical seismic source model derived by Blake (1952). It is estimated that 75 percent of the seismic energy in the primary waves is contained in the first half cycle of the ground displacement as shown on the seismograms from instruments located between 0.3 and 10 km from the explosion. The geometrical attenuation of the radiation field of the displacement wave is probably closely approximated by spherical divergence at ranges near the explosion. There is some evidence that a long-period displacement field may exist near the explosion as predicted by the theoretical model. However, there are not sufficient empirical data from the gnome explosion to make a detailed comparison between theory and observation.

Seismic source model for moving vehicles

2005 ◽  
Vol 43 (2) ◽  
pp. 248-256 ◽  
Author(s):  
S.A. Ketcham ◽  
M.L. Moran ◽  
J. Lacombe ◽  
R.J. Greenfield ◽  
T.S. Anderson
Keyword(s):  
Seismic Source ◽  
Source Model ◽  
Moving Vehicles ◽  
Seismic Source Model

On the Nature of Logic Trees in Probabilistic Seismic Hazard Assessment

2012 ◽  
Vol 28 (3) ◽  
pp. 1291-1296 ◽  
Author(s):  
Roger Musson
Keyword(s):  
Seismic Hazard Assessment ◽  
Seismic Source ◽  
Source Model ◽  
Probabilistic Seismic Hazard Assessment ◽  
Motion Model ◽  
Logic Tree ◽  
Ground Motion Model ◽  
Seismic Source Model ◽  
Kolmogorov Axioms ◽  
Better Than

An objection sometimes made against treating the weights of logic tree branches as probabilities relates to the Kolmogorov axioms, but these are only an obstacle if one believes that logic tree branches represent a seismic source model or ground motion model as being “true.” Models are never true, but some models are better than others. It is argued here that a logic tree weight represents the probability that the model in question is better than the others considered. Only one branch can be the best one, and one branch must be the best one. It is also argued that there are situations in PSHA where uncertainty exists but the analyst lacks the means to express it. Therefore it is not necessarily the case that more information increases uncertainty; it may be that more information increases the possibility of expressing uncertainty that was previously unmanageable.

The great Mexican earthquake of 19 June 1858: Expected ground motions and damage in Mexico City from a similar future event

1996 ◽  
Vol 86 (6) ◽  
pp. 1655-1666 ◽  
Author(s):  
S. K. Singh ◽  
M. Ordaz ◽  
L. E. Pérez-Rocha
Keyword(s):  
Mexico City ◽  
Transfer Functions ◽  
Ground Motions ◽  
Careful Examination ◽  
Great Earthquake ◽  
Normal Faulting ◽  
Cocos Plate ◽  
Current Design ◽  
Peak Horizontal Acceleration ◽  
The City

Abstract The description of the great earthquake of 19 June 1858 is unusual: damage and high intensities were reported both in the state of Michoacan and in Mexico City. Although a coastal epicenter for this earthquake cannot be ruled out, the reports agree better with an intermediate-depth (about 50 km), normal-faulting event in the subducted Cocos plate. A careful examination of the reports of this event and other normal-faulting events below the Mexican altiplano suggests that a likely location is 18.0 °N, 100.8 °W, near the epicenter of the 6 June 1964 (M7.3, H = 55 km) event. This location is 220 km SW of the city. The magnitude of the earthquake is estimated to be about 7.7. We synthesize expected ground motions in CU, a hill-zone site in the city, from an event similar to that of 1858, using records from the 23 May 1994 earthquake (18.0 °N, 100.6 °W, H = 50 km, M5.7) as an empirical Green's function and stress parameter, Δσ, of 50, 160, and 300 bar. The expected peak horizontal acceleration in CU of Δσ = 160 bar is about 30 gals. Similar acceleration was recorded in CU during the 1985, Michoacan earthquake (M8.0). We compute expected ground motions at many sites in Mexico City using empirical transfer functions and random vibration theory and compare these motions and the expected damage in the city with those from the 1985 Michoacan earthquake. Results show that the overall expected damage during the postulated earthquake is ⅔ and 1⅓ of that during the Michoacan earthquake for Δσ = 160 and 300 bar, respectively. A greater percentage of low-rise construction, which constitute about 80% of the total in the city, will be damaged during the postulated earthquake than during the Michoacan earthquake. The expected ground motions for Δσ = 50 bar are smaller at all periods than those from the Michoacan earthquake. As the present building code for Mexico City contemplates coastal earthquakes of magnitude greater than 8.0, the case of Δσ = 50 bar is not of interest in this article. This preliminary study suggests a need for a more careful evaluation of expected ground motion in the Valley of Mexico from the postulated earthquake and its impact on the current design spectra of the city.

Developing a seismic source model for the Arabian Plate

2018 ◽  
Vol 11 (15) ◽  
Author(s):  
I. El-Hussain ◽  
Y. Al-Shijbi ◽  
A. Deif ◽  
A. M. E. Mohamed ◽  
M. Ezzelarab
Keyword(s):  
Seismic Source ◽  
Source Model ◽  
Arabian Plate ◽  
Seismic Source Model

scholarly journals Ground Water Induced Changes in Velocities of P and S Waves (Vp and Vs) Measured Using Accurately Controlled Seismic Source

2020 ◽  
Author(s):  
Rina Suzuki ◽  
Koshun Yamaoka ◽  
Shuhei Tsuji ◽  
Toshiki Watanabe
Keyword(s):  
Ground Water ◽  
Seismic Waves ◽  
Crack Density ◽  
Seismic Source ◽  
Initial Response ◽  
Vibration Source ◽  
Water Mixture ◽  
S Waves ◽  
Fluid Saturation ◽  
Induced Changes

Abstract We analyzed the temporal variation in the travel times of both the P and S waves (Vp and Vs) for 14 months at Toyohashi (central Japan) with a continuously operating vibration source that could produce both P and S waves efficiently. The seismic waves produced by the source, which is named ACROSS (accurately-controlled routinely-operated signal system), were recorded by three nearby seismic stations, and the travel time variation at each station was calculated using the transfer function calculated from the recorded data. We observed the seasonal variations in the Vp and Vs for all the stations—which can be interpreted using the change in the fluid saturation and crack density of subsurface rocks—are consistent with the variation in the ground water level. The short-term responses to rainfall are observed at the nearest station; the interpretation of the changes in crack density and saturation is inconsistent with the ground water observation partly due the initial response to rainfall. This can be interpreted as an air-water mixture within pores or cracks on a fine scale.

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