The Whittier Narrows, California Earthquake of October 1, 1987—Early Results of Isoseismal Studies and Damage Surveys

1988 ◽  
Vol 4 (1) ◽  
pp. 1-10 ◽  
Author(s):  
E. V. Leyendecker ◽  
L. M. Highland ◽  
M. Hopper ◽  
E. P. Arnold ◽  
P. Thenhaus ◽  
...  
Keyword(s):  
Los Angeles ◽  
Field Survey ◽  
Ground Motions ◽  
Geographical Area ◽  
Mail Survey ◽  
Strong Motion ◽  
Peak Acceleration ◽  
Early Results ◽  
Acceleration Data ◽  
Strong Ground

Preliminary isoseismals for Modified Mercalli intensities are presented for the Whittier Narrows Earthquake. Isoseismals for intensities VI and lower are based on responses to a mail survey. Intensity VII and larger are based on a field survey of damage described in this paper. The maximum observed intensity of VIII was confined to Whittier. The shapes of the intensity contours compare favorably with the distribution of average peak acceleration data from the strong motion array in the greater Los Angeles area. The damage assessments appeared consistent with earthquake magnitude. However, the accelerations were higher than expected for the magnitude. The building classification and survey strategies developed were tested and found usable and adequate for describing damage. With further refinement this system can be used to describe damage within a limited geographical area and in a format useful for correlations with strong ground motions and the Modified Mercalli Intensity scale.

The 23 October 2011 MW7.0 Van (Eastern Turkey) Earthquake: Interpretations of Recorded Strong Ground Motions and Post-Earthquake Conditions of Nearby Structures

2014 ◽  
Vol 30 (2) ◽  
pp. 657-682 ◽  
Author(s):  
V. Akansel ◽  
G. Ameri ◽  
A. Askan ◽  
A. Caner ◽  
B. Erdil ◽  
...  
Keyword(s):  
Fault Plane ◽  
Ground Motions ◽  
Hanging Wall ◽  
Strong Motion ◽  
Thrust Fault ◽  
Building Structures ◽  
Epicentral Area ◽  
Historical Structures ◽  
Strict Compliance ◽  
Strong Ground

A major thrust-fault earthquake of MW = 7.0 occurred on 23 October 2011 at 10:41:21 UTC in the eastern Anatolian region of Turkey, severely affecting the nearby towns of Van and Erciş. In this study, a few strong-motion records from the epicentral area are analyzed in order to investigate the characteristics of the ground motions. Also reported are the post-earthquake field observations for various types of structures, such as buildings, bridges, historical structures, tunnels, and dams within the vicinity of the fault plane. The spatial distribution of damage indicates a noticeable hanging-wall effect. The special-type structures are observed to experience far less damage, as opposed to the building structures in the region pointing to the need for strict compliance to seismic building code and the corresponding construction requirements.

The Whittier Narrows, California Earthquake of October 1, 1987—Preliminary Analysis of Peak Horizontal Acceleration

1988 ◽  
Vol 4 (1) ◽  
pp. 115-137 ◽  
Author(s):  
K. W. Campbell
Keyword(s):  
Los Angeles ◽  
Hard Rock ◽  
Ground Motions ◽  
Ground Level ◽  
Topographic Effects ◽  
Peak Acceleration ◽  
Deep Soil ◽  
Horizontal Acceleration ◽  
Attenuation Relationships ◽  
Peak Horizontal Acceleration

The Ml=5.9 Whittier Narrows, California, earthquake triggered several hundred accelerographs in the greater Los Angeles area. One-hundred and sixty-eight of these were used to develop attenuation relationships for peak horizontal acceleration. The analysis indicates that the attenuation of peak acceleration during the earthquake was generally consistent with that predicted from the attenuation relationships of Campbell (in press). However, the acceleration amplitudes were about 65-percent higher than predicted. An analysis of residuals clearly showed that the ground motions recorded during this earthquake were influenced by a complex interaction of source mechanism, building embedment, site geology, and geography. Source effects may have been responsible for the higher-than-expected accelerations as well as some of the observed azimuthal variation. The correlation of peak acceleration with geography may have been caused in part by the gross geologic structure of the region. Buildings with basements were observed to have lower accelerations than ground-level sites, consistent with previous results. Accelerations from rock sites—especially those from hard rock sites—were found to have lower amplitudes and greater variability than those from soil sites. The larger variability may be due in part to topographic effects. All sites located within about 20 km of the fault recorded about the same level of acceleration whether they were sited on deep soil, soft rock, or hard rock. Shallow-soil sites, however, had higher-than-average accelerations at relatively short distances, but lower-than-average accelerations at longer distances. Their behavior at long distances was more consistent with that of the underlying rock rather than that of the overlying soil, no doubt reflecting the longer wavelengths of the more distant ground motions.

The Whittier Narrows, California Earthquake of October 1, 1987—CSMIP Strong Motion Data

1988 ◽  
Vol 4 (1) ◽  
pp. 75-100 ◽  
Author(s):  
A. Shakal ◽  
M. J. Huang ◽  
T. Q. Cao
Keyword(s):  
Los Angeles ◽  
Strong Motion ◽  
Suspension Bridge ◽  
State University ◽  
Peak Acceleration ◽  
Ground Response ◽  
Data Set ◽  
Strong Motion Records ◽  
Motion Data ◽  
Soft Story

The Whittier Narrows earthquake of October 1, 1987 generated the largest set of strong-motion records ever obtained from a single earthquake. The California Strong Motion Instrumentation Program (CSMIP) recovered 128 strong-motion records from 101 stations. Of these 101 stations, 63 are ground-response stations and 38 are extensively-instrumented structures. The structures include 27 buildings, eight dams, a suspension bridge, an airport tower, and a power plant. This paper summarizes that data set and highlights records of particular interest. The duration of strong shaking was approximately 3 to 4 seconds at most stations. The maximum peak acceleration values in the CSMIP data set are 0.62 g on the ground and 0.54 g in a structure. The largest acceleration (0.62 g) was recorded at a station near Tarzana, approximately 45 km from the epicenter. Other records of particular interest discussed here include the record from a soft-story building on the Los Angeles State University campus and the records from the Vincent Thomas suspension bridge near Long Beach. Digitization and processing of the accelerograms are underway, and accelerograms from 12 ground-response stations have been digitized as of this writing. The spectra show that the motion at the Tarzana station was dominated by 3 Hz energy. Spectra from other sites are relatively flat and do not show this spectral peak. The attenuation of peak acceleration with distance for this earthquake is compared with the relationship of Joyner and Boore (1981) derived from past earthquakes. On average, the peak acceleration data from this earthquake are higher than would be predicted by the Joyner-Boore model.

Modeling of source rupture characteristics for the Saguenay earthquake of November 1988

1995 ◽  
Vol 85 (2) ◽  
pp. 525-551 ◽  
Author(s):  
R. A. W. Haddon
Keyword(s):  
North America ◽  
Stress Drop ◽  
High Stress ◽  
Strong Motion ◽  
Eastern North America ◽  
Fault Rupture ◽  
Rupture Area ◽  
Past Half Century ◽  
Acceleration Data ◽  
Strong Ground

Abstract The magnitude mb = 6.0 Saguenay earthquake of 25 November 1988 in Quebec, Canada, was one of the largest to have occurred in eastern North America during the past half-century. Recorded high-frequency ground motions exceeded anticipated values for an event of its size by a factor of 10 on both the regional network and strong-motion instruments. Two proposed explanations for the discrepancy are (1) that the source was a rare “high stress drop” event and (2) that it was an asymmetrical “fractional stress drop” rupture (involving only normal effective stresses). In this article, detailed fault-slip models are derived to fit characteristics of strong-motion displacement, velocity, and acceleration data. The results establish that the effective rupture stress was normal (less than 100 bars), that the fault rupture was highly asymmetrical with respect to the point of rupture initiation, and that the average slip time for points within the rupture area (approx. 0.2 sec) was considerably less than that associated with the standard Brune (1970) source spectral model. The rupture area developed in a number of episodes, each widening or lengthening the previously ruptured area, which may explain the short average slip time. The results indicate that the widely used assumption in hazard analyses that earthquake spectra are adequately represented by the standard Brune (1970) complete stress drop model may be seriously unreliable for prediction of strong ground motion in eastern North America.

scholarly journals The calculation of horizontal accelerations from seismoscope records

1973 ◽  
Vol 63 (5) ◽  
pp. 1637-1661
Author(s):  
Ronald F. Scott
Keyword(s):  
Vibration Mode ◽  
Ground Motions ◽  
Strong Motion ◽  
Shaking Table ◽  
Watch Glass ◽  
San Fernando ◽  
Input Acceleration ◽  
Earthquake Vibration ◽  
Two Degree Of Freedom ◽  
Strong Ground

abstract The seismoscope is a simple instrument designed originally to give a largely qualitative indication of the strong ground motions produced by an earthquake. It consists of a smoked watch glass attached to a two-degree-of-freedom pendulum with a period of 34 sec and damping about 10 per cent of critical; a pen records the pendulum motions on the watch glass. One point on the displacement spectrum of the recorded ground motion at this period and damping is obtained from the measurement of the maximum pendulum excursion. An examination of the seismoscope record obtained on the east abutment of the failed Lower San Fernando dam during the 1971 San Fernando earthquake showed a high-frequency vibration superimposed on the general oscillations. It did not seem likely that this was solely an earthquake vibration component, and shaking table tests of seismoscopes revealed the presence of a seismoscope vibration mode at frequencies of 15 to 18 Hz depending on the instrument. The oscillations due to this mode on the abutment seismocope record have, therefore, been used as timing marks, to enable the seismoscope equation to be solved for the input acceleration components. The results of the calculations are presented along with analyses of the seismoscope response to indicate the range of applicability. One other record, obtained on a seismoscope alongside a strong-motion accelerograph, was also analyzed for comparison with the recorded accelerations, to demonstrate the validity of the technique. The timing vibration appears on a number of seismoscope records.

scholarly journals CHARACTERISTICS OF EARTHQUAKES IN THE MEXICAN SUBDUCTION ZONE ON STRONG MOTION ACCELEROGRAMS

1996 ◽  
pp. 17
Author(s):  
John Anderson ◽  
Roberto Quaas ◽  
Quigbin Chen ◽  
David Almora ◽  
Ricardo Vázquez ◽  
...  
Keyword(s):  
Strong Motion ◽  
Large Earthquake ◽  
Cascade Model ◽  
Peak Acceleration ◽  
Short Pulses ◽  
Wave Trains ◽  
Source Dimension ◽  
Large Earthquakes ◽  
Strong Ground ◽  
Weak Peak

Aceelerograms recorded on the Guerrero, Mexico, strong motion accelerograph network illustrate the dependence of strong ground motion on the magnitude and the hypocenter distance. These data suppport the hipothesis that complexity in accelerograms at short distances arises from complexity at the source. The duration of strong shaking is controlled by the source dimension at short distances, and  extended by wave porpagation effects as distance increases. Peak amplitudes (peak acceleration, velocity)  saturate at different magnitudes at different distances. This change in shape of attenuation curves as magnitude increases can be explained by the trnasition of Green's functions from simple, short pulses at short distances to longer duration wave trains at large distances. Spectral amplitudes demonstrate scalin relations in which loe frequency amplitudes are proportional to seismic moment but high frecuencies increase much less rapidly. The beginnings of large earthquakes look like small earthquakes, consistent with a cascade model for the growth of large events. The mostrecent large earthquake, on sept. 14,995 (Mw=7.4) shows surprisingly weak peak accelerations.

Strong-motion accelerograms of the Oroville aftershocks and peak acceleration data

1978 ◽  
Vol 68 (3) ◽  
pp. 677-689
Author(s):  
Linda C. Seekins ◽  
Thomas C. Hanks
Keyword(s):  
Source Region ◽  
Focal Depth ◽  
Strong Motion ◽  
Apparent Magnitude ◽  
Peak Acceleration ◽  
Acceleration Phase ◽  
Mean Values ◽  
Acceleration Data ◽  
Wide Range ◽  
Site Classes

abstract In the 90 days following the Oroville, California, earthquake (August 1, 1975; ML = 5.7), 313 positively identified strong-motion accelerograms were obtained for 86 different aftershocks. This set of records samples a wide range of magnitude (1.8 ≦ ML ≦ 5.2), focal depth (2 ≦ h ≦ 12 km), and site conditions (Holocene alluvium to Mesozoic crystalline basement). Most of these records were written at hypocentral distances R ≦ 15 km, a distance range for which relatively few strong-motion accelerograms had previously been available. Equally significant is the completeness of coverage (seven or more positively identified records) available for each of 12 well-recorded aftershocks (2.8 ≦ ML ≦ 4.9). One hundred and sixty-five peak acceleration values at 6.7 ≦ R ≦ 15 km for 33 aftershocks (3.0 ≦ ML ≦ 4.9) are the basis of an investigation of the dependence of peak acceleration on magnitude at R ≃ 10 km. These observations are supplemented with one datum for the main shock, 6 observations for two ML ≧ 5 aftershocks, and 61 null observations. Peak accelerations at sites on bedrock or minor sedimentary thicknesses are consistently higher than those at sites on several hundred meters or more of sedimentary rocks. Mean values for both site classes of data increase fairly rapidly with magnitude for 3 ≦ ML < 5, but the little available data for ML ≧ 5 suggest this magnitude dependence abruptly terminates at ML ≃ 5. The magnitude dependence of the sedimentarysite data is apparently stronger than for the bedrock-site data. Much if not all of the apparent magnitude dependence of these data can be attributed to properties of the path and not the source, consistent with the hypothesis that the amplitude of the peak acceleration phase, as it leaves the source region, does not depend on source strength although the predominant frequency of this phase increases as the duration and magnitude of the earthquake decreases.

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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