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.

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

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.

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.

Estimation of strong ground motions in meizoseismal region of the 1976 Tangshan, China, earthquake

1993 ◽  
Vol 83 (6) ◽  
pp. 1756-1777
Author(s):  
K. Dan ◽  
T. Ishii ◽  
M. Ebihara
Keyword(s):  
Earthquake Engineering ◽  
Ground Motions ◽  
Vertical Acceleration ◽  
Fault Models ◽  
Strong Ground Motions ◽  
Horizontal Acceleration ◽  
China Earthquake ◽  
Property Losses ◽  
Largest Aftershock ◽  
Strong Ground

Abstract The 1976 Tangshan, China, earthquake of MS 7.8 killed 242,000 persons, seriously injured 164,000 persons, and caused direct property losses totaling 8 billion Yuan Ren Min Bi (US $4.3 billion). Few investigations have been performed to estimate the characteristics of the strong ground motions in the meizoseismal region of this earthquake using either seismological or earthquake engineering approaches. In this paper, the observed far-field accelerograms of the mainshock are simulated by using the records of the second largest aftershock of MS 6.9 as Green's functions in order to obtain appropriate fault models for the mainshock. The strong ground motions in the meizoseismal region of the mainshock are then estimated by using these fault models and the records of several aftershocks with a magnitude of about 5 which were observed at temporary stations in the damaged area. The results indicate that large horizontal acceleration responses over 1000 cm/sec2 and vertical acceleration responses over 2000 cm/sec2 acted on the structures with natural periods shorter than 0.1 sec in the wide meizoseismal region having a length of 90 km.

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.

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.

Stress Drop Derived from Spectral Analysis Considering the Hypocentral Depth in the Attenuation Model: Application to the Ridgecrest Region, California

2021 ◽  
Author(s):  
Dino Bindi ◽  
Hoby N. T. Razafindrakoto ◽  
Matteo Picozzi ◽  
Adrien Oth
Keyword(s):  
Stress Drop ◽  
Spectral Decomposition ◽  
Epicentral Distance ◽  
Source Parameters ◽  
S Wave ◽  
Qualitative Comparison ◽  
Ground Shaking ◽  
Attenuation Model ◽  
Hypocentral Distance ◽  
The Impact

ABSTRACT We investigate the impact of considering a depth-dependent attenuation model on source parameters assessed through a spectral decomposition. In particular, we evaluate the effect of considering the hypocentral depth as an additional variable for the attenuation model, using as the target the tendency of the average stress drop to increase with depth, as observed in recent studies. We analyze the Fourier spectra of S-wave windows for about 1900 earthquakes with a magnitude above 2.5 recorded in the Ridgecrest region, southern California. Two different parameterizations of the attenuation term are implemented in the spectral decomposition, either as a function of the hypocentral distance alone or as a function of both epicentral distance and depth. The comparison of the spectral attenuation curves shows that, although the hypocentral model describes, on average, the range of values spanned by the attenuation curve for different depths, systematic differences with distance, depth, and frequency are observed. These differences are transferred to the source spectra and, in turn, to the source parameters extracted from the best-fitting ω−2 models. In particular, stress drops for events deeper than 7 km are, on average, almost double even when depth is introduced explicitly in the attenuation model. The increase of stress drop with depth is confirmed also after accounting for the increase of the shear velocity with depth, which absorbs about 30%–40% of the total increase. Moreover, a qualitative comparison with a model for the gradient of the effective normal stress confirms the reliability of the observed trend. Finally, the coherent spatial patterns shown by a simplified 2D tomographic representation of the spectral residuals highlights the impact on ground-shaking variability of the lateral variability of the crustal attenuation properties in the region.

Duration of nuclear explosion ground motion

1978 ◽  
Vol 68 (4) ◽  
pp. 1133-1145
Author(s):  
Walter W. Hays ◽  
Kenneth W. King ◽  
Robert B. Park
Keyword(s):  
Epicentral Distance ◽  
Ground Motions ◽  
Broad Band ◽  
Time History ◽  
Ground Acceleration ◽  
Ground Shaking ◽  
Distance Range ◽  
Nuclear Explosions ◽  
Dependent Site ◽  
Strong Ground

abstract This paper evaluates the duration of strong ground shaking that results from nuclear explosions and identifies some of the problems associated with its determination. Knowledge of the duration of horizontal ground shaking is important out to epicentral distances of about 44 km and 135 km, the approximate distances at which the ground shaking level falls to 0.01 g for nuclear explosions having yields of about 100 kt and 1,000 kt, respectively. Evaluation of the strong ground motions recorded from the event STRAIT (ML = 5.6) on a linear array of five, broad-band velocity seismographs deployed in the distance range 3.2 to 19.5 km provides information about the characteristics of the duration of ground shaking. The STRAIT data show that: (1) the definition that is used for defining duration is very important; (2) the duration of ground acceleration, as defined in terms of 90 per cent of the integral of the squared time history (Trifunac and Brady, 1975), increased from about 4 to 26 sec over the approximately 20-km distance range; and (3) the duration of ground velocity and displacement were slightly greater because of the effect of the alluvium layer on the propagating surface waves. Data from other events (e.g., MILROW, CANNIKIN, HANDLEY, PURSE) augment the STRAIT data and show that: (1) duration of shaking is increased by frequency-dependent site effects and (2) duration of shaking, as defined by the integral of the squared time history, does not increase as rapidly with increase in yield as is indicated by other definitions of duration that are stated in terms of an amplitude threshold (e.g., bracketed duration, response envelopes). The available data suggest that the duration of ground acceleration, based on the integral definition, varies from about 4 to 40 sec for a 100-kt range explosion and from about 4 to 105 sec for a megaton range explosion in the epicentral distance range of 0 to 44 km and 0 to 135 km, respectively.

The great Mexican earthquake of 19 June 1858: Expected ground motions and damage in Mexico City from a similar future event

1996 ◽  
Vol 86 (6) ◽  
pp. 1655-1666 ◽  
Author(s):  
S. K. Singh ◽  
M. Ordaz ◽  
L. E. Pérez-Rocha
Keyword(s):  
Mexico City ◽  
Transfer Functions ◽  
Ground Motions ◽  
Careful Examination ◽  
Great Earthquake ◽  
Normal Faulting ◽  
Cocos Plate ◽  
Current Design ◽  
Peak Horizontal Acceleration ◽  
The City

Abstract The description of the great earthquake of 19 June 1858 is unusual: damage and high intensities were reported both in the state of Michoacan and in Mexico City. Although a coastal epicenter for this earthquake cannot be ruled out, the reports agree better with an intermediate-depth (about 50 km), normal-faulting event in the subducted Cocos plate. A careful examination of the reports of this event and other normal-faulting events below the Mexican altiplano suggests that a likely location is 18.0 °N, 100.8 °W, near the epicenter of the 6 June 1964 (M7.3, H = 55 km) event. This location is 220 km SW of the city. The magnitude of the earthquake is estimated to be about 7.7. We synthesize expected ground motions in CU, a hill-zone site in the city, from an event similar to that of 1858, using records from the 23 May 1994 earthquake (18.0 °N, 100.6 °W, H = 50 km, M5.7) as an empirical Green's function and stress parameter, Δσ, of 50, 160, and 300 bar. The expected peak horizontal acceleration in CU of Δσ = 160 bar is about 30 gals. Similar acceleration was recorded in CU during the 1985, Michoacan earthquake (M8.0). We compute expected ground motions at many sites in Mexico City using empirical transfer functions and random vibration theory and compare these motions and the expected damage in the city with those from the 1985 Michoacan earthquake. Results show that the overall expected damage during the postulated earthquake is ⅔ and 1⅓ of that during the Michoacan earthquake for Δσ = 160 and 300 bar, respectively. A greater percentage of low-rise construction, which constitute about 80% of the total in the city, will be damaged during the postulated earthquake than during the Michoacan earthquake. The expected ground motions for Δσ = 50 bar are smaller at all periods than those from the Michoacan earthquake. As the present building code for Mexico City contemplates coastal earthquakes of magnitude greater than 8.0, the case of Δσ = 50 bar is not of interest in this article. This preliminary study suggests a need for a more careful evaluation of expected ground motion in the Valley of Mexico from the postulated earthquake and its impact on the current design spectra of the city.

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