Comparison of earthquake and microtremor ground motions in El Centro, California

1973 ◽  
Vol 63 (4) ◽  
pp. 1227-1253 ◽  
Author(s):  
F. E. Udwadia ◽  
M. D. Trifunac
Keyword(s):  
Site Response ◽  
Ground Motions ◽  
Strong Motion ◽  
Site Conditions ◽  
Ground Shaking ◽  
Response Characteristics ◽  
Local Site ◽  
Simple Features ◽  
Low Amplitude ◽  
Local Site Conditions

abstract Strong earthquake ground shaking has been investigated by the study of 15 events recorded in El Centro, California. The strong-motion records analyzed show that no simple features (e.g., local site conditions) govern the details of local ground shaking. Any effects of local subsoil conditions at this site appear to be overshadowed by the source mechanism and the transmission path, there being no distinctly identifiable site periodicities. Microtremor measurements have been taken in the area surrounding the strong-motion site. The objective was an investigation of possible correlations with strong ground motions and the analysis of site-response characteristics. Basic difficulties in ascertaining local site conditions through such low-amplitude ground motions are illustrated. It has been found that in this area microtremor and earthquake processes are widely different in character, there being little to no correlation between the ground's response to earthquakes and to microtremor excitations. Microtremors have been found to be nonstationary over periods of about a day or so, introducing further uncertainties into inferences from such measurements.

scholarly journals On correlation of seismoscope response with earthquake magnitude and Modified Mercalli Intensity

1975 ◽  
Vol 65 (2) ◽  
pp. 307-321
Author(s):  
M. D. Trifunac ◽  
A. G. Brady
Keyword(s):  
Strong Motion ◽  
Quantitative Measure ◽  
Relative Displacement ◽  
Earthquake Magnitude ◽  
Western United States ◽  
Site Conditions ◽  
Local Site ◽  
Local Earthquake ◽  
Local Earthquake Magnitude ◽  
Local Site Conditions

abstract A quantitative measure of the Modified Mercalli Intensity Scale for earthquakes in the western United States has been developed by correlating the peak seismoscope relative displacement response, Sd, with the reported site intensity, IMM. This correlation can be approximated by S ̄ d ( cm ) ≈ 1 49.2 10 0.288 I MM for IMM ≦ VIII and is characterized by one standard deviation of about 0.7 S̄d. The data used in this study do not indicate an obvious type of dependence of Sd on local site conditions. A method for computing the analog of the local earthquake magnitude, Mseismoscope, has been presented for possible use in strong-motion seismology and for scaling earthquakes by close-in measuremients, when other seismological instruments may go off scale.

scholarly journals The 30 October 2020 Samos (Eastern Aegean Sea) Earthquake: effects of source rupture, path and local-site conditions on the observed and simulated ground motions

2021 ◽  
Author(s):  
Aybige Akinci ◽  
Daniele Cheloni ◽  
AHMET ANIL DINDAR
Keyword(s):  
Ground Motion ◽  
Structural Damage ◽  
Ground Motions ◽  
Aegean Sea ◽  
Peak Ground Velocity ◽  
Ground Shaking ◽  
Local Site ◽  
Eastern Aegean ◽  
Motion Characteristics ◽  
Eastern Aegean Sea

Abstract On 30 October 2020 a MW 7.0 earthquake occurred in the eastern Aegean Sea, between the Greek island of Samos and Turkey’s Aegean coast, causing considerable seismic damage and deaths, especially in the Turkish city of Izmir, approximately 70 km from the epicenter. In this study, we provide a detailed description of the Samos earthquake, starting from the fault rupture to the ground motion characteristics. We first use Interferometric Synthetic Aperture Radar (InSAR) and Global Positioning System (GPS) data to constrain the source mechanisms. Then, we utilize this information to analyze the ground motion characteristics of the mainshock in terms of peak ground acceleration (PGA), peak ground velocity (PGV), and spectral pseudo-accelerations. Modelling of geodetic data shows that the Samos earthquake ruptured a NNE-dipping normal fault located offshore north of Samos, with up to 2.5-3 m of slip and an estimated geodetic moment of 3.3 ⨯ 1019 Nm (MW 7.0). Although low PGA were induced by the earthquake, the ground shaking was strongly amplified in Izmir throughout the alluvial sediments. Structural damage observed in Izmir reveals the potential of seismic risk due to the local site effects. To better understand the earthquake characteristics, we generated and compared stochastic strong ground motions with the observed ground motion parameters as well as the ground motion prediction equations (GMPEs), exploring also the efficacy of the region-specific parameters which may be improved to better predict the expected ground shaking from future large earthquakes in the region.

Pitfalls of Deterministic Application of Nonlinear Site Factors in Probabilistic Assessment of Ground Motions

2009 ◽  
Vol 25 (3) ◽  
pp. 541-555 ◽  
Author(s):  
Christine A. Goulet ◽  
Jonathan P. Stewart
Keyword(s):  
Site Effects ◽  
Site Response ◽  
Ground Motions ◽  
Site Conditions ◽  
Return Periods ◽  
Site Factors ◽  
Intensity Measures ◽  
Site Specific ◽  
Nonlinear Site Response ◽  
Rock And Soil

It is common for ground motions to be estimated using a combination of probabilistic and deterministic procedures. Probabilistic seismic hazard analyses (PSHA) are performed to estimate intensity measures ( IMs) for reference site conditions (usually rock). This is followed by a deterministic modification of the rock IMs to account for site effects, typically using site factors from the literature or seismic codes. We demonstrate for two California sites and three site conditions that the deterministic application of nonlinear site factors underestimates ground motions evaluated probabilistically for return periods of engineering interest. Reasons for this misfit include different standard deviation terms for rock and soil sites, different controlling earthquakes, and overestimation of the nonlinear component of the site response in the deterministic procedure. This problem is solved using site-specific PSHA with appropriate consideration of nonlinear site response, within the hazard integral.

scholarly journals Limits on the potential accuracy of earthquake risk evaluations using the L’Aquila (Italy) earthquake as an example

2015 ◽  
Vol 58 (2) ◽  
Author(s):  
John Douglas ◽  
Daniel Monfort Climent ◽  
Caterina Negulescu ◽  
Agathe Roullé ◽  
Olivier Sedan
Keyword(s):  
Strong Motion ◽  
Earthquake Risk ◽  
Calibration Data ◽  
Building Vulnerability ◽  
Potential Accuracy ◽  
Ground Shaking ◽  
Local Site ◽  
Damage States ◽  
Macroseismic Intensities ◽  
Strong Motion Network

<p>This article is concerned with attempting to ‘predict’ (hindcast) the damage caused by the L’Aquila 2009 earthquake (M<sub>w</sub> 6.3) and, more generally, with the question of how close predicted damage can ever be to observations. Damage is hindcast using a well-established empirical-based approach based on vulnerability indices and macroseismic intensities, adjusted for local site effects. Using information that was available before the earthquake and assuming the same event characteristics as the L’Aquila mainshock, the overall damage is reasonably well predicted but there are considerable differences in the damage pattern. To understand the reasons for these differences, information that was only available after the event were include within the calculation. Despite some improvement in the predicted damage, in particularly by the modification of the vulnerability indices and the parameter influencing the width of the damage distribution, these hindcasts do not match all the details of the observations. This is because of local effects: both in terms of the ground shaking, which is only detectable by the installation of a much denser strong-motion network and a detailed microzonation, and in terms of the building vulnerability, which cannot be modeled using a statistical approach but would require detailed analytical modeling for which calibration data are likely to be lacking. Future studies should concentrate on adjusting the generic components of the approach to make them more applicable to their location of interest. To increase the number of observations available to make these adjustments, we encourage the collection of damage states (and not just habitability classes) following earthquakes and also the installation of dense strong-motion networks in built-up areas.</p>

scholarly journals Anomalous transients in GPS measurements due to induced changes in local site conditions

2019 ◽  
Vol 128 (7) ◽  
Author(s):  
Sandeep Gupta ◽  
Paresh Nath Singharoy ◽  
Rajeev Kumar Yadav ◽  
Joshi K Catherine ◽  
Roland Burgmann ◽  
...  
Keyword(s):  
Site Conditions ◽  
Gps Measurements ◽  
Local Site ◽  
Induced Changes ◽  
Local Site Conditions
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