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31 results on '"Beroza, G. C."'

7. Earthquake Seismology: An Introduction and Overview

Author

Beroza, G. C., Kanamori, H., Beroza, G. C., and Kanamori, H.

Abstract

This introductory chapter covers the science of earthquake seismology: the study of earthquakes using seismic waves. In it, we touch on some of the many interesting and varied research questions that earthquake seismology seeks to address. We begin by reviewing the basic understanding of where, why, and how earthquakes occur in the context of the theory of plate tectonics. Earthquakes have had, and will continue to have, an important impact on human affairs, so it is natural to note some of the more significant earthquakes in history, as gauged by different measures, while doing this. From here, we delve into more quantitative aspects of earthquake source theory and how seismologists use the radiated wave field to understand the mechanics of earthquakes and faulting. The wide range of temporal and spatial scales that are important to the faulting process mean that there are necessarily a wide range of approaches and perspectives in the study of earthquakes. In this overview chapter, we can only give them cursory treatment, but subsequent chapters explore these different perspectives in detail. We end the overview by introducing research issues in the closely related fields of tsunami generation, Nuclear Test Ban Treaty verification, and earthquake risk mitigation. All of these are closely intertwined with the science of earthquake seismology.

Published
2015

8. Predicción del movimiento del suelo de fuentes de terremotos realistas utilizando el campo sísmico ambiental

Author

Denolle, M. A., Dunham, E. M., Prieto, G. A., and Beroza, G. C.

Subjects
Radiation pattern, Ground motion prediction, Green's functions, Ambient noise, Spectral collocation, Surface waves, Physics::Geophysics
Abstract

Predicting accurate ground motion is critical for earthquake hazard analysis, particularly in situations where sedimentary basins trap and amplify seismic waves. We exploit the information carried by the ambient seismic field to extract surface?wave Green's functions between seismic stations and to predict long?period ground motion from earthquakes. To do so, we modify the surface impulse response to correct for the source depth and for the double?couple focal mechanism. These corrections are derived under the assumption that material properties in the immediate vicinity of the source depend only on depth. Using this local 1?D assumption, we solve the surface?wave eigenproblem and compute the fundamental?mode displacement eigenfunctions to express the surface?wave excitation at the source. We validate this technique, which we call the virtual earthquake approach, by comparing computed seismograms with earthquake waveforms from four moderate earthquakes that occur near broadband stations in southern California. The depth and mechanism corrections show clear improvements of the predicted ground motion relative to the surface impulse response.

Published
2013

30. The nature of the landers-mojave earthquake line.

Author

Nur A, Ron H, and Beroza GC

Abstract

The Landers, California, earthquake of 28 June 1992 (magnitude = 7.3) is the latest of six significant earthquakes in the past 60 years whose epicenters and slip directions define a 100-kilometer alignment running approximately N15 degrees W across the central Mojave region. This pattern may indicate a geologically young throughgoing fault that replaces numerous older strike-slip faults by obliquely cutting across them. These older faults, and perhaps also the bend in the San Andreas fault, may be losing their ability to accommodate upper crustal deformation because they have become unfavorably oriented with respect to the regional stress field.

Published
1993
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31. Mechanism diversity of the loma prieta aftershocks and the mechanics of mainshock-aftershock interaction.

Author

Beroza GC and Zoback MD

Abstract

The diverse aftershock sequence of the 1989 Loma Prieta earthquake is inconsistent with conventional models of mainshock-aftershock interaction because the aftershocks do not accommodate mainshock-induced stress changes. Instead, the sense of slip of the aftershocks is consistent with failure in response to a nearly uniaxial stress field in which the maximum principal stress acts almost normal to the mainshock fault plane. This orientation implies that (i) stress drop in the mainshock was nearly complete, (ii) mainshock-induced decreases of fault strength helped were important in controlling the occurrence of after-shocks, and (iii) mainshock rupture was limited to those sections of the fault with preexisting shear stress available to drive fault slip.

Published
1993
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