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.

On the characteristics of local geology and their influence on ground motions generated by the Loma Prieta earthquake in the San Francisco Bay region, California

1992 ◽  
Vol 82 (2) ◽  
pp. 603-641 ◽  
Author(s):  
Roger D. Borcherdt ◽  
Gary Glassmoyer
Keyword(s):  
Ground Motion ◽  
San Francisco ◽  
San Francisco Bay ◽  
Ground Motions ◽  
Loma Prieta Earthquake ◽  
Franciscan Complex ◽  
Horizontal Acceleration ◽  
Geological Conditions ◽  
Peak Horizontal Acceleration ◽  
Loma Prieta

Abstract Strong ground motions recorded at 34 sites in the San Francisco Bay region from the Loma Prieta earthquake show marked variations in characteristics dependent on crustal structure and local geological conditions. Peak horizontal acceleration and velocity inferred for sites underlain by “rock” generally occur on the transverse component of motion. They are consistently greater with lower attenuation rates than the corresponding mean value predicted by empirical curves based on previous strong-motion data. Theoretical amplitude distributions and synthetic seismograms calculated for 10-layer models suggest that “bedrock” motions were elevated due in part to the wide-angle reflection of S energy from the base of a relatively thin (25 km) continental crust in the region. Characteristics of geologic and geotechnical units as currently mapped for the San Francisco Bay region show that average ratios of peak horizontal acceleration, velocity and displacement increase with decreasing mean shear-wave velocity. Ratios of peak acceleration for sites on “soil” (alluvium, fill/Bay mud) are statistically larger than those for sites on “hard rock” (sandstone, shale, Franciscan Complex). Spectral ratios establish the existence of predominant site periods with peak amplifications near 15 for potentially damaging levels of ground motion at some sites underlain by alluvium and fill/bay mud. Average spectral amplifications inferred for vertical and the mean horizontal motion are, respectively, (1,1) for sites on the Franciscan Complex (KJf), (1.4, 1.5) for sites on Mesozoic and Tertiary rocks (TMzs), (2.1, 2.0) for sites on the Santa Clara Formation (QTs), (2.3, 2.9) for sites on alluvium (Qal), and (2.1, 4.0) for sites on fill/Bay mud (Qaf/Qhbm). These mean values are not statistically different at the 5% significance level from those inferred from previous low-strain data. Analyses suggest that soil amplification and reflected crustal shear energy were major contributors to levels of ground motion sufficient to cause damage to vulnerable structures at distances near 100 km in the cities of San Francisco and Oakland.

scholarly journals PROPERTIES OF THE GROUND MOTIONS PARAMETERS NEAR THE EARTHQUAKE FOCUS

2016 ◽  
Author(s):  
К.С. Харебов ◽  
А.Н. Баскаев ◽  
Ш.С. Хубежты
Keyword(s):  
Data Base ◽  
Extreme Point ◽  
Epicentral Distance ◽  
Ground Motions ◽  
Statistical Significance ◽  
Vertical Acceleration ◽  
Earthquake Focus ◽  
Hypocentral Distance ◽  
Horizontal Acceleration ◽  
Peak Horizontal Acceleration

Представлены дополнения в базу данных сильных движений: введены записи за 2015 г. с интенсивностью от 5 баллов, а также записи с эпицентральным расстоянием не больше 7 км с любой интенсивностью. Проведено исследование зависимости средних значений параметров грунтовых движений от гипоцентрального расстояния в ближней зоне землетрясения в интервалах: 0–5, 5–10, 10–15, 15–20, 20–25, 25–30, 30–40, 40–50, 0–50, 50–2000, 0–2000 км. Проведена оценка статистической значимости зависимостей. Показано, что параметры грунтовых движений имеют экстремальную точку при гипоцентральных расстояниях около 20 км, которую можно считать границей между ближней и дальней зоной землетрясения. Показано, что отношение пикового вертикального ускорения к пиковому горизонтальному ускорению (PVA/PHA) коррелирует с магнитудой события – чем выше магнитуда, тем больше значение PVA/PHA при равных прочих условиях Additions into the Strong Motions Data Base are represented: records 2015 year with the intensity from 5, and also the records with epicentral distance not greater than 7 km with any intensity. A study of the ground motions parameters average values dependence on the hypocentral distance in the neighbor zone of earthquake in the intervals: 0–5, 5–10, 10–15, 15–20, 25–30, 30–40, 40–50, 0–50, 50–2000, 0–2000 km is carried out. The estimation of the statistical significance of dependences is carried out. It is shown that the parameters of ground motions have the extreme point with the hypocentral distances about 20 km, which can be considered as the boundary between the near and far zone of earthquake. It is shown that the ratio of peak vertical acceleration to the peak horizontal acceleration (PVA/PHA) correlates with the magnitude of event – the higher the magnitude, the greater the value PVA/PHA under otherwise equal conditions.

Peak acceleration, velocity, and displacement from strong-motion records

1980 ◽  
Vol 70 (1) ◽  
pp. 305-321
Author(s):  
David M. Boore ◽  
William B. Joyner ◽  
Adolph A. Oliver ◽  
Robert A. Page
Keyword(s):  
Regression Analysis ◽  
Peak Velocity ◽  
Strong Motion ◽  
Western North America ◽  
Peak Acceleration ◽  
Motion Data ◽  
Horizontal Acceleration ◽  
Large Structures ◽  
San Fernando ◽  
Peak Horizontal Acceleration

abstract Strong-motion data from earthquakes of western North America are examined to provide the basis for estimating peak acceleration, velocity, and displacement as a function of distance for three magnitude classes, 5.0 to 5.7, 6.0 to 6.4, and 7.1 to 7.6. Analysis of a subset of the data from the San Fernando earthquake shows that small but statistically significant differences exist between peak values of horizontal acceleration, velocity, and displacement recorded on soil at the base of small structures and values recorded at the base of large structures. The peak acceleration tends to be less and the peak velocity and displacement to be greater at the base of large structures than at the base of small structures. In the distance range used in the regression analysis (15 to 100 km), the values of peak horizontal acceleration recorded at soil sites in the San Fernando earthquake are not significantly different from the values recorded at rock sites, but values of peak horizontal velocity and displacement are significantly greater at soil sites.

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.

scholarly journals INFLUENCE OF THE SOILS TYPES ON THE STRONG GROUND MOTIONS INTENSITY

2015 ◽  
Author(s):  
А.Н. Баскаев ◽  
К.С. Харебов
Keyword(s):  
Wave Speed ◽  
Ground Motions ◽  
Correlation Dependence ◽  
Hypocentral Distance ◽  
Strong Ground Motions ◽  
Horizontal Acceleration ◽  
Different Types ◽  
Peak Horizontal Acceleration ◽  
Strong Ground ◽  
Different Soils

Проведено исследование влияния различных видов грунтов на интенсивность проявления сильных грунтовых движений на примере записей базы данных, созданной авторами. Для различных типов грунта (скала, песок, гравий, ил, глина) получены корреляционные зависимости интенсивности от логарифма пикового горизонтального ускорения и от гипоцентрального расстояния по отдельности. Показано, что при высоких магнитудах интенсивность проявляется на различных грунтах в порядке убывания следую- щим образом: глина, песок, ил, гравий, скала. Проведенное исследование показало слабую зависимость интенсивности от скорости поперечной волны. Проведеное сравнение корреляционных зависимостей интенсивности от магнитуды и от гипоцентрального расстояния для записей базы данных SMDBCGI с уравнением Шебалина, показало что точность формулы авторов для всех типов грунтов и формулы Шебалина одинакова в пределах ошибки. Показано, что для станций системы KNET лучше использовать формулу корреляционной зависимости интенсивности от магнитуды и от логарифма пикового горизонтального ускорения, чем от магнитуды и от логарифма гипоцентрального расстояния Study of the different soils forms influence on the intensity of the strong ground motions manifestation based on the records data base, created by the authors is carried out. The correlation dependences of intensity on the logarithm of peak horizontal accelerationandon the hypocentral distance separately are obtained for different types of soil (rock, sand, gravel, silt, clay). For the different groundswith the high magnitudes the intensity valueis in follows descending order: clay, sand, silt, gravel, rock. The conducted investigation showed the weak dependence of intensity on the transverse wave speed. The comparison of the correlation dependences of intensity on the magnitude and on the hypocentral distance for records of database SMDB CGI with Shebalin formula showed thatthe accuracy of the authors formula for all types of grounds and Shebalin formula is identical in the ranges of error. For the system KNET stations it is better to use the formula of correlation dependence of intensity on the magnitude and on the logarithm of peak horizontal acceleration, than the correlation dependence on the magnitude and on the hypocentral distance logarithm

Strong ground motion from the Uttarkashi, Himalaya, India, earthquake: Comparison of observations with synthetics using the composite source model

1995 ◽  
Vol 85 (1) ◽  
pp. 31-50 ◽  
Author(s):  
G. Yu ◽  
K. N. Khattri ◽  
J. G. Anderson ◽  
J. N. Brune ◽  
Y. Zeng
Keyword(s):  
Ground Motions ◽  
Source Model ◽  
Seismic Gap ◽  
Main Central Thrust ◽  
Strong Ground Motions ◽  
Velocity Models ◽  
Horizontal Acceleration ◽  
Peak Horizontal Acceleration ◽  
Composite Source Model ◽  
Strong Ground

Abstract The Uttarkashi earthquake of 19 October 1991 (MS = 7.0) occurred in the greater Himalayan region north of the main central thrust, at an estimated depth of 12 km. The fault plane solution indicates a low-angle thrust mechanism, striking northwest, consistent with the tectonic pattern of thrusting in the region. Aftershocks define a belt parallel to, and north of, the surface trace of the main central thrust, roughly 10-km wide and 30-km long. The mainshock is located at the northeast edge of this zone. The earthquake was recorded on 13 strong-motion accelerographs at distances ranging from 25 to 150 km from the epicenter. One station at Bhatwari (peak horizontal acceleration of 272 cm sec−2) is above the aftershock zone. The maximum peak horizontal acceleration was about 313 cm sec−2 at Uttarkashi, at an epicentral distance of 36 km. The amplitudes and frequency content of the strong ground motions are more or less consistent with expectations for an earthquake of this magnitude in California. Synthetics generated using the composite source model and synthetic Green's functions (Zeng et al., 1994a, b) are successful in producing acceleration, velocity, and displacement with a realistic appearance and the correct statistical properties of the two accelerograms recorded nearest the fault (Bhatwari and Uttarkashi). To produce these, we introduced trial-and-error modifications of the layered-medium velocity model within uncertainties. At more distant stations, we first used the velocity structure that worked for the two nearest stations. Differences emphasize the large potential role of unknown site and wave-propagation effects. For the station at Tehri, we explored different velocity models, and found one there that was also quite successful. We then used these two velocity models to predict strong ground motions at Bhatwari and Tehri, from a potential magnitude 8.5 earthquake filling part of the seismic gap along the Himalayan frontal faults. The synthetics show peak accelerations that are only somewhat larger than those in the Uttarkashi event, but much longer durations and increased amplitudes of response spectra at long periods.

A subset of CyberShake ground-motion time series for response-history analysis

2021 ◽  
pp. 875529302098197
Author(s):  
Jack W Baker ◽  
Sanaz Rezaeian ◽  
Christine A Goulet ◽  
Nicolas Luco ◽  
Ganyu Teng
Keyword(s):  
Time Series ◽  
Los Angeles ◽  
Seismic Hazard ◽  
Ground Motion ◽  
Ground Motions ◽  
Response Spectra ◽  
Motion Time ◽  
History Analysis ◽  
Response History Analysis ◽  
Simulated Ground Motions

This manuscript describes a subset of CyberShake numerically simulated ground motions that were selected and vetted for use in engineering response-history analyses. Ground motions were selected that have seismological properties and response spectra representative of conditions in the Los Angeles area, based on disaggregation of seismic hazard. Ground motions were selected from millions of available time series and were reviewed to confirm their suitability for response-history analysis. The processes used to select the time series, the characteristics of the resulting data, and the provided documentation are described in this article. The resulting data and documentation are available electronically.

scholarly journals Ground motions in urban Los Angeles from the 2019 Ridgecrest earthquake sequence

2021 ◽  
pp. 875529302110039
Author(s):  
Filippos Filippitzis ◽  
Monica D Kohler ◽  
Thomas H Heaton ◽  
Robert W Graves ◽  
Robert W Clayton ◽  
...  
Keyword(s):  
Los Angeles ◽  
Ground Motion ◽  
Ground Motions ◽  
Earthquake Sequence ◽  
Motion Prediction ◽  
Ground Motion Prediction Equations ◽  
Prediction Equations ◽  
Ground Motion Prediction ◽  
Velocity Models ◽  
Spectral Accelerations

We study ground-motion response in urban Los Angeles during the two largest events (M7.1 and M6.4) of the 2019 Ridgecrest earthquake sequence using recordings from multiple regional seismic networks as well as a subset of 350 stations from the much denser Community Seismic Network. In the first part of our study, we examine the observed response spectral (pseudo) accelerations for a selection of periods of engineering significance (1, 3, 6, and 8 s). Significant ground-motion amplification is present and reproducible between the two events. For the longer periods, coherent spectral acceleration patterns are visible throughout the Los Angeles Basin, while for the shorter periods, the motions are less spatially coherent. However, coherence is still observable at smaller length scales due to the high spatial density of the measurements. Examining possible correlations of the computed response spectral accelerations with basement depth and Vs30, we find the correlations to be stronger for the longer periods. In the second part of the study, we test the performance of two state-of-the-art methods for estimating ground motions for the largest event of the Ridgecrest earthquake sequence, namely three-dimensional (3D) finite-difference simulations and ground motion prediction equations. For the simulations, we are interested in the performance of the two Southern California Earthquake Center 3D community velocity models (CVM-S and CVM-H). For the ground motion prediction equations, we consider four of the 2014 Next Generation Attenuation-West2 Project equations. For some cases, the methods match the observations reasonably well; however, neither approach is able to reproduce the specific locations of the maximum response spectral accelerations or match the details of the observed amplification patterns.

scholarly journals Attenuation relationships of peak ground motions in the Jazan Region

2021 ◽  
Vol 14 (3) ◽  
Author(s):  
Ali K. Abdelfattah ◽  
Abdullah Al-amri ◽  
Kamal Abdelrahman ◽  
Muhamed Fnais ◽  
Saleh Qaysi
Keyword(s):  
Saudi Arabia ◽  
Ground Motions ◽  
Prediction Equation ◽  
Peak Ground Velocity ◽  
Local Magnitude ◽  
Ground Acceleration ◽  
Data Set ◽  
Hypocentral Distance ◽  
Distance Range ◽  
Attenuation Relationships

AbstractIn this study, attenuation relationships are proposed to more accurately predict ground motions in the southernmost part of the Arabian Shield in the Jazan Region of Saudi Arabia. A data set composed of 72 earthquakes, with normal to strike-slip focal mechanisms over a local magnitude range of 2.0–5.1 and a distance range of 5–200 km, was used to investigate the predictive attenuation relationship of the peak ground motion as a function of the hypocentral distance and local magnitude. To obtain the space parameters of the empirical relationships, non-linear regression was performed over a hypocentral distance range of 4–200 km. The means of 638 peak ground acceleration (PGA) and peak ground velocity (PGV) values calculated from the records of the horizontal components were used to derive the predictive relationships of the earthquake ground motions. The relationships accounted for the site-correlation coefficient but not for the earthquake source implications. The derived predictive attenuation relationships for PGV and PGA are$$ {\log}_{10}(PGV)=-1.05+0.65\cdotp {M}_L-0.66\cdotp {\log}_{10}(r)-0.04\cdotp r, $$ log 10 PGV = − 1.05 + 0.65 · M L − 0.66 · log 10 r − 0.04 · r , $$ {\log}_{10}(PGA)=-1.36+0.85\cdotp {M}_L-0.85\cdotp {\log}_{10}(r)-0.005\cdotp r, $$ log 10 PGA = − 1.36 + 0.85 · M L − 0.85 · log 10 r − 0.005 · r , respectively. These new relationships were compared to the grand-motion prediction equation published for western Saudi Arabia and indicate good agreement with the only data set of observed ground motions available for an ML 4.9 earthquake that occurred in 2014 in southwestern Saudi Arabia, implying that the developed relationship can be used to generate earthquake shaking maps within a few minutes of the event based on prior information on magnitudes and hypocentral distances taking into considerations the local site characteristics.

Peak horizontal acceleration and velocity from strong-motion records including records from the 1979 imperial valley, California, earthquake

1981 ◽  
Vol 71 (6) ◽  
pp. 2011-2038 ◽  
Author(s):  
William B. Joyner ◽  
David M. Boore
Keyword(s):  
Strong Motion ◽  
Fault Rupture ◽  
Imperial Valley ◽  
Attenuation Relations ◽  
Motion Data ◽  
Horizontal Acceleration ◽  
Anelastic Attenuation ◽  
Distance Dependence ◽  
Peak Horizontal Acceleration

Abstract We have taken advantage of the recent increase in strong-motion data at close distances to derive new attenuation relations for peak horizontal acceleration and velocity. This new analysis uses a magnitude-independent shape, based on geometrical spreading and anelastic attenuation, for the attenuation curve. An innovation in technique is introduced that decouples the determination of the distance dependence of the data from the magnitude dependence. The resulting equations are log A = − 1.02 + 0.249 M − log r − 0.00255 r + 0.26 P r = ( d 2 + 7.3 2 ) 1 / 2 5.0 ≦ M ≦ 7.7 log V = − 0.67 + 0.489 M − log r − 0.00256 r + 0.17 S + 0.22 P r = ( d 2 + 4.0 2 ) 1 / 2 5.3 ≦ M ≦ 7.4 where A is peak horizontal acceleration in g, V is peak horizontal velocity in cm/ sec, M is moment magnitude, d is the closest distance to the surface projection of the fault rupture in km, S takes on the value of zero at rock sites and one at soil sites, and P is zero for 50 percentile values and one for 84 percentile values. We considered a magnitude-dependent shape, but we find no basis for it in the data; we have adopted the magnitude-independent shape because it requires fewer parameters.

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