The Mexico Earthquake of September 19, 1985—Effect of Magnitude on the Character of Strong Ground Motion: An Example from the Guerrero, Mexico Strong Motion Network

1988 ◽  
Vol 4 (3) ◽  
pp. 635-646 ◽  
Author(s):  
J. G. Anderson ◽  
R. Quaas
Keyword(s):  
Subduction Zone ◽  
Ground Motion ◽  
Strong Ground Motion ◽  
Strong Motion ◽  
Earthquake Source ◽  
Hypocentral Distance ◽  
Source Theory ◽  
Mexico Earthquake ◽  
Strong Motion Network ◽  
Strong Ground

The Guerrero digital accelerograph network has been operating, since spring of 1985, on rock sites along the coast of Mexico, above an active subduction zone. The accelerograms collected through June 1987 include examples from events with magnitudes from 3 to 8, all recorded at nearly the same hypocentral distance. Spectra from these accelerograms scale in a manner that is qualitatively consistent with earthquake source theory. Based on four selected events, peak accelerations attenuate more rapidly for small events than for large events.

30 Ooctober 2020 Samos-Sigacik Earthquake: On Strong Ground Motion and Local Site Amplification

2021 ◽  
Author(s):  
Eser Çakti ◽  
Karin Sesetyan ◽  
Ufuk Hancilar ◽  
Merve Caglar ◽  
Emrullah Dar ◽  
...  
Keyword(s):  
Ground Motion ◽  
Structural Damage ◽  
Strong Ground Motion ◽  
Epicentral Distance ◽  
Strong Motion ◽  
Aegean Sea ◽  
Site Amplification ◽  
Local Site ◽  
Basin Effects ◽  
Strong Ground

<p>The Mw 6.9 earthquake that took place offshore between the Greek island of Samos and Turkey’s İzmir province on 30 October 2020 came hardly as a surprise. Due to the extensional tectonic regime of the Aegean and high deformation rates, earthquakes of similar size frequently occur in the Aegean Sea on fault segments close to the shores of Turkey, affecting the settlements on mainland Turkey and on the Greek Islands. Samos-Sigacik earthquake had a normal faulting mechanism. It was recorded by the strong motion networks in Turkey and Greece. Although expected, the earthquake was an  outstanding event in the sense of  highly localized, significant levels of building damage as a result of amplified ground motion levels. This presentation is an overview of strong ground motion characteristics of this important event both regionally and locally. Mainshock records suggest that local site effects, enhanced by basin effects could be responsible for structural damage in central Izmir, the third largest city of Turkey located at 60-70 km epicentral distance. We installed a seven-station network in Bayraklı and Karşıyaka districts of İzmir within three days of the mainshock in search of site and basin effects.  Through analysis of recorded aftershocks we explore the amplification characeristics of soils in the two aforementioned districts  and try to understand the role basin effects might have played in the resulting ground motion levels and consequently damage. </p>

scholarly journals ESTIMATION OF NEAR-SOURCE STRONG GROUND MOTION FROM LARGE SUBDUCTION ZONE EARTHQUAKE

2006 ◽  
Vol 62 (4) ◽  
pp. 877-890
Author(s):  
Atsushi NOZU ◽  
Shogo MIYAJIMA ◽  
Go NAKANISHI ◽  
Masayuki YAMADA
Keyword(s):  
Subduction Zone ◽  
Ground Motion ◽  
Strong Ground Motion ◽  
Subduction Zone Earthquake ◽  
Strong Ground

The Loma Prieta earthquake, ground motion, and damage in Oakland, Treasure Island, and San Francisco

1991 ◽  
Vol 81 (5) ◽  
pp. 2019-2047
Author(s):  
Thomas C. Hanks ◽  
A. Gerald Brady
Keyword(s):  
Ground Motion ◽  
San Francisco ◽  
Strong Ground Motion ◽  
Strong Motion ◽  
Earthquake Ground Motion ◽  
Transverse Motion ◽  
Loma Prieta Earthquake ◽  
Loma Prieta ◽  
Treasure Island ◽  
Strong Ground

Abstract The basis of this study is the acceleration, velocity, and displacement wave-forms of the Loma Prieta earthquake (18 October 1989; M = 7.0) at two rock sites in San Francisco, a rock site on Yerba Buena Island, an artificial-fill site on Treasure Island, and three sites in Oakland underlain by thick sections of poorly consolidated Pleistocene sediments. The waveforms at the three rock sites display a strong coherence, as do the three sedimentary sites in Oakland. The duration of strong motion at the rock sites is very brief, suggestive of an unusually short source duration for an earthquake of this size, while the records in Oakland show strong amplification effects due to site geology. The S-wave group at Treasure Island is phase coherent with the Oakland records, but at somewhat diminished amplitudes, until the steps in acceleration at approximately 15 sec, apparently signaling the onset of liquefaction. All seven records clearly show shear-wave first motion opposite to that expected for the mainshock radiation pattern and peak amplitudes greater than expected for sites at these distances (95 ± 3 km) from an earthquake of this magnitude. While the association between these ground motion records and related damage patterns in nearby areas has been easily and eagerly accepted by seismological and engineering observers of them, we have had some difficulty in making such relationships quantitative or even just clear. The three Oakland records, from sites that form a nearly equilateral triangle about the Cypress Street viaduct collapse, are dominated by a long-period resonance (≃ 1 1/2-sec period) far removed from the natural frequency of the structure to transverse motion (2.5 Hz) or from high-frequency amplification bands observed in aftershock studies. A spectral ratio arbiter of this discrepancy confuses it further. The failure of the East Bay crossing of the San Francisco-Oakland Bay Bridge cannot be attributed to relative displacements of the abutments in Oakland and Yerba Buena Island, but the motions of the Bay Bridge causing failure remain unknown. The steps in acceleration at Treasure Island present unusual strong-motion accelerogram processing problems, and modeling suggests that the velocity and displacement waveforms are contaminated by a spurious response of the filtering operations to the acceleration steps. A variety of coincidences suggests that the Treasure island accelerogram is the most likely strong-motion surrogate for the filled areas of the Marina District, for which no mainshock records are available, but the relative contributions of bad ground, poor construction and truly strong ground motion to damage in the Marina District will never by known in any quantitative way. The principal lesson of all of this is that until a concerted effort is mounted to instrument ground and structures that are likely to fail during earthquakes, our understanding of the very complex relationships between strong ground motion and earthquake damage will, in general, remain rudimentary, imprecise, and vague.

Estimation of attenuation relations for strong-motion data allowing for individual earthquake magnitude uncertainties

1997 ◽  
Vol 87 (6) ◽  
pp. 1674-1678
Author(s):  
David A. Rhoades
Keyword(s):  
Ground Motion ◽  
Regression Models ◽  
Strong Ground Motion ◽  
Strong Motion ◽  
Error Variance ◽  
Attenuation Relations ◽  
Motion Data ◽  
Different Levels ◽  
Magnitude Determination ◽  
Strong Ground

Abstract Standard errors of earthquake magnitudes are routinely calculated and vary appreciably between earthquakes. However, the uncertainties of magnitude determination are usually ignored in regression models of strong ground motion as a function of magnitude and distance from the earthquake source. This practice has the potential to bias estimates of strong ground motion. A method is given for taking account of the uncertainty of each magnitude determination in fitting such models. It extends previous methods in which the error variance is partitioned into between-earthquake and within-earthquake components. It allows for further decomposition of the between-earthquake component into a part attributable to magnitude uncertainties and a part attributable to other causes. The method has been applied to the well-known attenuation data of Joyner and Boore (1981). The Mw determinations in this dataset fall into two subsets with distinctly different levels of precision, namely, those determined directly and those inferred from values of ML. It is shown that most of the between-earthquake component of variance can be attributed to the relatively low precision of the magnitudes in the latter subset.

Empirical Attenuation Equations for Vertical Ground Motion in Turkey

2004 ◽  
Vol 20 (3) ◽  
pp. 853-882 ◽  
Author(s):  
Erol Kalkan ◽  
Polat Gülkan
Keyword(s):  
Ground Motion ◽  
Strong Ground Motion ◽  
Strong Dependence ◽  
Strong Motion ◽  
Vertical Acceleration ◽  
Data Set ◽  
Attenuation Relationships ◽  
Geological Conditions ◽  
Ground Motion Records ◽  
Strong Ground

In the aftermath of two destructive urban earthquakes in 1999 in Turkey, empirical models of strong motion attenuation relationships that have been previously developed for North American and European earthquakes have been utilized in a number of national seismic hazard studies. However, comparison of empirical evidence and estimates present significant differences. For that reason, a data set created from a suite of 100 vertical strong ground motion records from 47 national earthquakes that occurred between 1976 and 2002 has been used to develop attenuation relationships for strong ground motion in Turkey. A consistent set of empirical attenuation relationships was derived for predicting vertical peak and pseudo-absolute vertical acceleration spectral ordinates in terms of magnitude, source-to-site distance, and local geological conditions. The study manifests the strong dependence of vertical to horizontal (V/H) acceleration ratio on spectral periods and relatively weaker dependence on site geology, magnitude, and distance. The V/H ratio is found to be particularly significant at the higher frequency end of the spectrum, reaching values as high as 0.9 at short distances on soil sites. The largest long-period spectral ratios are observed to occur on rock sites where they can reach values in excess of 0.5. These results raise misgivings concerning the practice of assigning the V/H ratio a standard value of two-thirds. Hence, nonconservatism of this value at short periods and its conservatism at long periods underline the need for its revision, at least for practice in Turkey.

scholarly journals Computer processing of New Zealand strong-motion accelerograms

1983 ◽  
Vol 16 (3) ◽  
pp. 234-246
Author(s):  
S. B. Hodder
Keyword(s):  
New Zealand ◽  
Ground Motion ◽  
Strong Ground Motion ◽  
Processing System ◽  
Strong Motion ◽  
Computer Processing ◽  
Band Pass ◽  
New Processing ◽  
Earthquake Accelerograms ◽  
Strong Ground

Recently implemented modifications to the computer processing of earthquake accelerograms are described. The main extensions to the system include dynamic instrument correction, robust band-pass filtering and accurate integration, all implemented in the frequency domain. The processed records now provide accurate representations of strong ground motion within the frequency band from 0.25 Hz to 24.5 Hz: full accuracy is maintained in the computed velocity and displacement signals. The use of the new processing system is demonstrated using two previously recorded accelerograms.

scholarly journals A decomposition of strong ground motion

1994 ◽  
Vol 27 (2) ◽  
pp. 124-128
Author(s):  
W.R. Stephenson
Keyword(s):  
Ground Motion ◽  
Strong Ground Motion ◽  
Strong Motion ◽  
Possible Cause ◽  
Strong Ground

The Cedar Hills Nursery strong motion record of the 1987 October 1st Whittier Narrows earthquake can be decomposed into five physically distinct components. These are the usual radial, circumferential and vertical components, plus a 2.84 Hz resonance along 317° N and a 3.27 Hz resonance along 317° N. The significance and possible cause of the resonant parts are discussed.

Earthquake Ground Motions: Implications for Designing Structures and Reconciling Structural Damage

1985 ◽  
Vol 1 (2) ◽  
pp. 239-270 ◽  
Author(s):  
Jogeshwar P. Singh
Keyword(s):  
Ground Motion ◽  
Strong Ground Motion ◽  
Ground Motions ◽  
Strong Motion ◽  
Soil Condition ◽  
Dominant Factor ◽  
Soil Conditions ◽  
Earthquake Ground Motions ◽  
Geological Conditions ◽  
Strong Ground

Until recently, characteristics of strong ground motion resulting from different soil conditions were considered the dominant factor in developing design ground motions and reconciling observed damage. Interpretation of recent recordings of earthquakes by strong motion instrument arrays installed in California and Taiwan show that basic characteristics of strong motion are greatly influenced by the seismological and geological conditions. For a given soil condition, the characteristics of strong ground motion (peak ground acceleration, peak ground velocity, peak ground displacement, duration, spectral content, and time histories) can vary significantly whether the site is near or far from the seismic source. As local soil conditions only modify the ground motions produced by a given source, variability in ground motion due to seismologic and geologic conditions (for a given soil condition) must be considered in estimating earthquake ground motions for structural design or for estimating structural vulnerabilities to reconcile earthquake-related damage.

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