Estimates Of Ground Acceleration Research Articles

Data-Driven Synthesis of Broadband Earthquake Ground Motions Using Artificial Intelligence

ABSTRACTRobust estimation of ground motions generated by scenario earthquakes is critical for many engineering applications. We leverage recent advances in generative adversarial networks (GANs) to develop a new framework for synthesizing earthquake acceleration time histories. Our approach extends the Wasserstein GAN formulation to allow for the generation of ground motions conditioned on a set of continuous physical variables. Our model is trained to approximate the intrinsic probability distribution of a massive set of strong-motion recordings from Japan. We show that the trained generator model can synthesize realistic three-component accelerograms conditioned on magnitude, distance, and VS30. Our model captures most of the relevant statistical features of the acceleration spectra and waveform envelopes. The output seismograms display clear P- and S-wave arrivals with the appropriate energy content and relative onset timing. The synthesized peak ground acceleration estimates are also consistent with observations. We develop a set of metrics that allow us to assess the training process’s stability and to tune model hyperparameters. We further show that the trained generator network can interpolate to conditions in which no earthquake ground-motion recordings exist. Our approach allows for the on-demand synthesis of accelerograms for engineering purposes.

Re-assessment of peak ground accelerations for large magnitude Vrancea intermediate-depth earthquakes

In this short paper, the peak ground acceleration estimates of four major Vrancea intermediate-depth earthquakes with moment magnitudes MW ≥ 6.9 which occurred in the twentieth century are re-assessed using a recently proposed procedure combining macroseismic intensity data with a ground motion model derived for this seismic source. An empirical relation between macroseismic intensity and peak ground acceleration is proposed in this study for Vrancea intermediate-depth earthquakes. The results show that the largest median updated peak ground accelerations are obtained in the case of the Vrancea MW 7.7 earthquake of November 1940. Moreover, for some cities, the updated peak ground accelerations are higher than the ones given in the current Romanian seismic design code. In addition, peak ground acceleration values in excess of 0.1 g are noticed for almost half of the Romanian territory in the case of the November 1940 and March 1977 Vrancea intermediate-depth seismic events.

Seismic hazard analysis for East Malaysia; based on a proposed ground motion prediction equation

The seismic hazard analysis requires an estimation of ground motion intensity where the process needs to use a compatible ground motion prediction equation or GMPE, which provides ground acceleration estimates in a function of earthquake magnitude and distance. Hence, the effect of current equation often does not accurately represent the earthquake condition in East Malaysia region. In this study, the characteristics of low-to-moderate databases were used and derived by regression analysis in terms of horizontal peak ground acceleration (PGA). The appropriate GMPE design for East Malaysia is based on the ground motion records compiled from strike slip earthquakes that occurred within 10 to 1,350 km. This earthquake data is based on actual data recorded at a broad range of magnitude levels within a wide range of distances. The new equation is used to predict the PGA value throughout East Malaysia by probabilistic method. PSHA is a method to analyse seismic hazard assessment using probability concept by considering the uncertainties of the size, location and rate of occurrence of earthquake and the variation of ground motion characteristics. The four well-known existing attenuation functions are evaluated with current equation to highlight their limitations in magnitude and distance. With a more complete collection of earthquake databases, GMPE has become more reliable. The GMPE of peak ground acceleration for low-to-moderate earthquake at long distance was found to be logarithmically distributed. The equation provides ease in both implementation and interpretation of physical parameters with a comparable standard deviation.

Preliminary Probabilistic Seismic Hazard Analysis of the CO2CRC Otway Project Site, Victoria, Australia

Abstract We present a preliminary probabilistic seismic hazard analysis (PSHA) of a site in the Otway basin, Victoria, Australia, as part of the CO2CRC Otway Project for CO 2 storage risk. The study involves estimating the likelihood of future strong earthquake shaking at the site and utilizes three datasets: (1) active faults, (2) historical seismicity, and (3) geodetic surface velocities. Our analysis of geodetic data reveals strain rates at the limit of detectability and not significantly different from zero. Consequently, we do not develop a geodetic-based source model for this Otway model. We construct logic trees to capture epistemic uncertainty in both the fault and seismicity source parameters and in the ground-motion prediction. A new feature for seismic hazard modeling in Australia, and rarely dealt with in low-seismicity regions elsewhere, is the treatment of fault episodicity (long-term activity versus inactivity) in our Otway model. Seismic hazard curves for the combined (fault and distributed seismicity) source model show that hazard is generally low, with peak ground acceleration estimates of less than 0.1 g at annual probabilities of 10 -3 -10 -4 /yr. Our preliminary analysis therefore indicates that the site is exposed to a low seismic hazard that is consistent with the intraplate tectonic setting of the region and unlikely to pose a significant hazard for CO 2 containment and infrastructure.

Assessment of Potential Seismic Damage to Residential Unreinforced Masonry Buildings in Northern Illinois

Ground acceleration estimates for northern Illinois are used to assess any damage that can occur to unreinforced masonry (URM) residential structures as a result of potential future earthquakes. These estimates are based on probable future activities in the New Madrid Seismic Zone and are published by the U.S. Geological Survey for exceedance probabilities equal to 0.10, 0.05, and 0.02 per 50 years. Accelerations corresponding to higher exceedance probabilities (1.0 and 0.25 probability in 50 years) are obtained from simplified seismic hazard analyses. Damage is estimated based on fragility curves available for URM buildings. The probability of damage is then used along with the inventory of buildings to arrive at estimates of the percentage and the number of buildings that may suffer damage of various levels (ranging from nonstructural damage to total collapse). The study shows that considering p=1 exceedance probability in 50 years (i.e., a 50 year return period), the maximum acceleration for the area w...

Effect of Soil Aging on Assessing Magnitudes and Accelerations of Prehistoric Earthquakes

Increase in strength due to aging of sands is reflected in higher blow counts and tip resistance values in penetration resistance measurements. This affects the magnitudes and peak ground acceleration estimates of prehistoric earthquakes obtained from an analysis of geotechnical observations at paleoliquefaction sites in the South Carolina Coastal Plain. In this study, corrections were made to account for the effects of soil aging, which were neglected in earlier estimates. The results show that when the effects of aging of soils on their geotechnical properties are incorporated, the resulting back-calculations reduced earlier magnitude estimates of prehistoric earthquakes by about 0.9 units. The peak ground acceleration estimates were reduced by about 15% for those earthquakes originally estimated at approximately 0.15 g. For those earthquakes whose original estimates were greater than 0.2 g, there was no noticeable change when a correction was made for the aging of soils.

Precarious rock evidence for low near-source accelerations for trans-tensional strike-slip earthquakes

This paper describes precarious rock evidence for low ground motions associated with extensional sections of strike-slip faults. Recent evidence from physical and numerical models and data regressions has indicated that ground motion for extensional strike-slip regions may be lower than for strike-slip faults with a large fault-normal tectonic stress component, and for thrust faults in general. Data from compressional strike-slip and thrust earthquakes dominates the database used in most regression curves for ground acceleration, and in the calculation of current probabilistic seismic hazard maps. Therefore, estimates of ground accelerations on these seismic hazard maps may be too high for sites near extensional sections of strike-slip faults. This paper discusses precariously balanced rock data from three areas near extensional sections of strike-slip faulting: (1) the region of the Honey fault, California, with an active Holocene fault, (2) the Red Rock Canyon region of the Garlock fault, near a dilatational step-over, and (3) the region just south of Beaumont, California, near the Hemet dilatational step-over in the San Jacinto fault. These are all active strike-slip faults, with at least a few large earthquakes in the Holocene, and, in the case of the San Jacinto example, historic large earthquakes ( M=7). Thus, the precarious rocks at these sites are evidence of relatively low ground motions associated with extensional strike-slip faulting. The results of this study could be very important in developing more detailed seismic hazard maps in the future.

Estimates of the ground accelerations at Point Reyes Station during the 1906 San Francisco earthquake

Abstract We have developed an analytical solution for the rocking and overturning response of a two-dimensional, symmetric rigid block subject to a full sine wave of horizontal ground acceleration. We use this solution to provide lower-bound estimates of the peak ground acceleration at Point Reyes Station, California, during the 1906 San Francisco earthquake that toppled the San Francisco-bound train. Our results, for a 3% damping ratio, indicate that for a single cycle of a sine wave the minimum toppling accelerations at 1, 1.5, and 2 Hz are 0.35g, 0.5g, and 1.05g, respectively. For more realistic accelerograms the toppling accelerations are about 1.1g (complex synthetic) and 0.76g (Lucerne record of the 1992 Landers earthquake).

Dynamic site response evaluation of the Port City of Aqaba (Jordan) employing the equivalent linear method

As part of an ongoing research program to develop local seismic engineering ground motion parameters for implementation in the Jordanian Seismic Building Code, a practical contribution is made to determine the local site coefficient (S) for the Port City of Aqaba, southern Jordan. Employing probabilistic peak ground acceleration estimates using FRISK, the overall dynamic site response design spectrum is obtained through the calculated response spectrum based on selected soil-rock column profiles applying SHAKE91. The parabolic shape of the S coefficient design spectrum is given by the following relationships:S = 1.06 for Tb/ Ts<= 0.56S = -0.81 + 4.68(Tb/ Ts) -2.38(Tb/ Ts)2for 0.56 < (Tb/ Ts)<=1.43S = 1.00 for Tb/ Ts>1.43where Tband Tsare the structural and site response design periods (in seconds), respectively.Key words: dynamic, site, response, Aqaba, spectrum, design.

Dynamic site response evaluation of the Port City of Aqaba (Jordan) employing the equivalent linear method

As part of an ongoing research program to develop local seismic engineering ground motion parameters for implementation in the Jordanian Seismic Building Code, a practical contribution is made to determine the local site coefficient (S) for the Port City of Aqaba, southern Jordan. Employing probabilistic peak ground acceleration estimates using FRISK, the overall dynamic site response design spectrum is obtained through the calculated response spectrum based on selected soil-rock column profiles applying SHAKE91. The parabolic shape of the S coefficient design spectrum is given by the following relationships:S = 1.06 for Tb / Ts <= 0.56S = -0.81 + 4.68(Tb / Ts) -2.38(Tb / Ts)2 for 0.56 < (Tb / Ts)<=1.43S = 1.00 for Tb / Ts >1.43where Tb and Ts are the structural and site response design periods (in seconds), respectively.Key words: dynamic, site, response, Aqaba, spectrum, design.

A structural analysis in seismic archaeology: the walls of Noto and the 1693 earthquake

A crucial problenl for seismic archeology is how to recognize seismic effects and how to date them. On an experimental basis. we proposed that the problem be reversed, and that we begin at the other end: i.e. by analyzing already known seismic effects on ancient structures, testified by written sources. to be able to .calibrate&gt;&gt; the types or possible observations and any subsequent elaborations. The choice of the walls of Noto was suggested by the fact that Noto was abandoned following the earthquake of l693 (I,= XI MCS. Me 7.5) which had already been studied in depth as part of an ING research programme (1988-92). Moreover, just after recent research, this event proved to be reconstructed with a high quality standard. Photogrammetric measurements were made on several parts of the town walls to plot a numerical model aimed at ascertaining specific aspects of the earthquake damage. An estimate of the ground acceleration during the earthquake has been attempted via non-linear finite-element analyses of a building located by the main city gate. The analyses show that. in order to obtain the building vault collapse, a ground acceleration of 0.5 to 0.7 g had to be reached during the earthquake. This result, typical of a strong earthquake such as the one of 1693, proves that an approach based on finite element analysis and a sound engineering judgment Inay be systematically applied to historical earthquake sites to obtain some estimates of ground acceleration in historical earthquakes. On the whole, this work aimed at starting up the second development phase of the great event of 1693 of which the macroseismic erfects are known. In the meantime, some possibilities of tackling structural analyses in seismic archaeology are being explored.

Nonstructural damage from the Northridge earthquake

The occurrence of the January 17, 1994, Northridge earthquake prompted site visits by teams of Canadian engineers to study the effects of the earthquake. This paper summarizes the observations of nonstructural damage to commercial, institutional, industrial, and utility facilities in the Northridge area. The performance of nonstructural components recorded in this paper is correlated to available estimates of ground acceleration at each site. Nonstructural damage was extensive throughout the area. The examples chosen include a broad range of representative damage. Some examples of well-performed systems are also included. Key words: earthquake, seismic, Northridge, nonstructural, codes, reconnaissance.