Estimated Peak Ground Acceleration Research Articles

Ground motion estimation during 25th April 2015 Nepal earthquake

In the absence of an array of strong motion records, numerical and empirical methods are used to estimate the ground motion during 25th April 2015 Nepal earthquake. Spectral finite element method is used to simulate low frequency displacements. First, the simulated ground displacement is compared with the recorded data at Kathmandu. The good agreement between the comparisons validates the input source and medium parameters. The spatial variation of ground displacement is depicted through peak ground displacement and Ground residual displacement (GRD) contours near the epicentral region. The maximum GRD is of the order of 0.6 m in east–west, 1.8 m in north–south and 0.6 m in vertical (Z) direction respectively. Stochastic finite fault seismological model is used to simulate acceleration time histories. First, the seismological model is calibrated for the region with the available strong ground motion records at Kathmandu. The estimated stress drop for main-event and aftershocks lie in between 50 and 95 bars. Acceleration time histories are simulated at several stations near the epicentral region. Peak ground acceleration (PGA) and spectral acceleration (Sa) contour maps are provided. The estimated PGA near the epicentral region varies from 0.3 to 0.05 g. Another estimate of PGA for the main event is obtained from damage reports. The estimated PGA from simulations and damage reports are observed to be consistent with each other. The average amplification in the Indo-Gangetic plain is estimated to be in the order of 2–6. The simulated results from the study can be used as the basis for the possible ground motion behaviour for a future earthquake of comparable magnitude in the Himalayan region.

Uncertainty in the estimates of peak ground acceleration in seismic hazard analysis

Probabilistic seismic hazard analysis has become a standard procedure preceding the antiseismic construction. An important component of the relevant calculations is the allowance for the uncertainty in the strong motion parameters (e.g., peak ground acceleration (PGA)). In the present-day approaches of probabilistic analysis, this uncertainty is modeled by a random variable (a residual) which has a lognormal distribution. With this model, the extrapolation into the area of long return periods yields nonzero probabilities of unrealistically high PGA. In the present work, the distribution of the logarithmic PGA residuals is modeled by different parametric distributions. From the set of these distributions, the one which provides the closest approximation of the empirical data is selected by the statistical criteria. The analysis shows that the generalized extreme value distribution (GEVD) most accurately reproduces the residuals of the logarithmic PGA, and the tail of the distribution is approximated by the generalized Pareto distribution (GPD).

Ground Motion Estimation Using Front Site Wave Form Data Based on RVM for Earthquake Early Warning

The use of the earthquake early warning system (EEWS), one of the most useful emergency response tools, requires that the accuracy of real-time ground motion prediction (GMP) be enhanced. This requires that waveform information at observation points along earthquake wave propagation paths (hereafter, front-site waveform information) be used effectively. To enhance the combined reliability of different systems, such as on-site and local/regional warning, we present a GMP method using front-site waveform information by applying a relevant vector machine (RVM). We present methodology and application examples for a case study estimating peak ground acceleration (PGA) and peak ground velocity (PGV) for earthquakes in the Miyagi-Ken Oki subduction zone. With no knowledge of source information, front site waveforms have been used to predict ground motion at target sites. Five input variables – earthquake PGA, PGD, pulse rise time, average period and theVpmax/Amaxratio – have been used for the first 4 to 6 seconds of P-waves in training a regression model. We found that RVM is a useful tool for the prediction of peak ground motion.

Seismic‐Hazard Map of Southeast Missouri and Likely Magnitude of the February 1812 New Madrid Earthquake

Abstract The New Madrid seismic zone lies beneath the upper Mississippi Embayment, straddling the border between southeastern Missouri and northwestern Tennessee. In late 1811 and early 1812, it produced five earthquakes of magnitudes >6.5, violently shaking the central and eastern United States (CEUS). Its magnitude and recurrence are of concern to today’s central United States regions. By considering the effects of local geology, deterministic scenario maps ( M w 7.3 and 7.7) were produced for ground motions intended to simulate the 7 February 1812 event (NM3), which was the largest felt. These maps include spatial estimates of peak ground acceleration and of 0.2 s and 1.0 s spectral acceleration (SA). Compared with the isoseismic map of modified Mercalli intensities (MMIs) in southeast Missouri, the MMIs converted from 0.2 s SA suggest that M w 7.7 is a plausible scenario for NM3. To better constrain its magnitude, other CEUS sites shaken during NM3 were also examined. Local site conditions were studied and evaluated before calculating the threshold magnitude for the reported MMIs. These results indicate that the magnitude of NM3 was at least M w 7.6, which validates our estimated size of M w 7.7 for southeastern Missouri.

Probabilistic Seismic‐Hazard Analysis for Central Java Province, Indonesia

The Central Java region is one of the most seismically active regions in Indonesia. Each year, the region experiences an average of more than 20 medium‐to‐large magnitude earthquakes. Hence, reliable hazard analysis is necessary for the region, and we undertook this study in order to conduct a probabilistic seismic‐hazard analysis to estimate and map peak ground acceleration (PGA) and spectral response at 0.2 and 1 s periods, with 10% probability of exceedance in 50 years corresponding to the return period of 475 years. Maps presented in this study are intended for regional purposes only and may be useful for emergency response planning and urban development. The database used in this study is compiled from the Indonesian Meteorological, Climatological, and Geophysical Agency, the U.S. Geological Survey, and the Incorporated Research Institutions for Seismology. The compiled catalog covers an area between latitude 5°–12° S and longitude 105°–115° E and includes moment magnitude 5 and greater from 1900 to February 2011. We used a standard logic‐tree approach that included systematic allowances for various seismicity models. Because a region‐specific empirical ground‐motion model is lacking, we used Next Generation Attenuation ground‐motion relations. We calculated PGA and spectral response at 0.2 and 1 s periods for all cities across Central Java. We found that the city of Pati is subject to the highest seismic hazard with a PGA of 0.45 g , and the city of Kendal has the lowest hazard with a PGA of 0.13 g . This study provides a basis upon which to design maps for building codes and emergency planning.

A Ground‐Motion Predictive Model for Iran and Turkey for Horizontal PGA, PGV, and 5% Damped Response Spectrum: Investigation of Possible Regional Effects

We present a ground‐motion prediction equation (GMPE) for Turkey and Iran to investigate the possible regional effects on ground‐motion amplitudes in shallow active crustal earthquakes. The proposed GMPE is developed from a subset of the recently compiled strong‐motion database of the Earthquake Model of the Middle East Region project (see [Data and Resources][1]). A total of 670 Turkish and 528 Iranian accelerograms with depths down to 35 km are used to estimate peak ground acceleration, peak ground velocity, and 5% damped elastic pseudospectral acceleration ordinates of 0.01 s≤ T ≤4 s. The moment magnitude range of the model is 4≤ M w≤8, and the maximum Joyner–Boore distance is R JB=200 km. The functional form considers three major fault mechanisms (strike slip, normal, and reverse). The nonlinear soil behavior is a function of V S 30 (average shear‐wave velocity in the upper 30 m of soil profile). Our observations from empirical and estimated ground‐motion trends advocate regional differences in the territories covered by Iran and Turkey that originate from the differences in Q factors, kappa, and near‐surface velocity profiles. These factors eventually affect the magnitude‐ and distance‐dependent scaling of spectral amplitudes in Iran and Turkey. In essence, the ground‐motion amplitudes of these two neighboring countries would draw patterns different than the ground‐motion estimates of GMPEs developed from the strong‐motion databases of shallow active crustal earthquakes from multiple countries. Online Material: MATLAB code and regression coefficients for computing the response spectrum and distance scaling. [1]: #sec-7

Fuzzy—probabilistic seismic hazard assessment, case study: Tehran region, Iran

This study presents a new model for probabilistic seismic hazard assessment based on fuzzy sets theory. To accomplish seismic hazard analysis in the framework of fuzzy sets theory, all of the variables are first converted into Gaussian fuzzy sets using α-cut method. Then, fuzzified variables are used in seismic hazard analysis. Finally, the outputs are defuzzified using center of area method. The method is applied to Tehran region, Iran, and the fuzzy hazard curve is obtained for the site. The curve displays a fuzzy-probabilistic estimate of peak ground acceleration (PGA) over bedrock for the various return periods. PGA values for the region are estimated to be 0.18–0.20 g and 0.42–0.48 g for 50- and 475-year return periods, respectively. The results are given as fuzzy intervals which accommodate the vagueness inherent in the data.

Probabilistic seismic hazard analysis of interconnected infrastructure: a case of Iranian high-pressure gas supply system

Seismic hazard maps are widely used for engineering design, land-use planning, and disaster mitigation. The development of the new seismic hazard map of Iran with regard to the specification of Iranian high-pressure gas network is based on probabilistic seismic hazard analysis using the historical and new earthquakes data, geology, tectonics, fault activity, and seismic zone models in Iran. The map displays the probabilistic estimates of peak ground acceleration for the return period of 2,475 year (2 % probability in 50 years). The results presented in this study will provide the basis for the preparation of risk map, the estimation of insurance premiums, finding best paths for future pipelines, planning, and relocating lifeline facilities especially for interconnected infrastructures.

Probabilistic seismic hazard assessment of Himachal Pradesh and adjoining regions

Seismically active Himachal Pradesh and adjoining regions comprising Himalayan orogenic belt with the experience of the great Kangra earthquake of 1905, has high potential for river valley projects. There are already operating hydropower projects, some under construction and a few more coming up. In view of this it is important to know the ground motion nature for various locales. The present study is about estimation of Peak Ground Acceleration (PGA) for the state of Himachal Pradesh and adjoining regions using probabilistic seismic hazard analysis (PSHA) approach. Standard procedure for PSHA has been adopted for this study and peak ground motion has been estimated for 10% and 2% probability of exceedance in 50 years at the bed rock level considering two cases: (i) varying b-value for each source zone, (ii) constant b-value for each source zone. For 10% probability of exceedance in 50 years, the PGA values vary from 0.096 to 0.15 g and 0.09 to 0.26 g considering varying b-value, and constant b-value, respectively. In case of 2% probability of exceedance in 50 years, the PGA varies between 0.07 to 0.24 g considering varying b-values and 0.14 to 0.37 g considering constant b-values. Higher PGA values are observed in the southeast part considering varying b-values whereas the region situated around Kaurik Fault System (KFS) has shown higher PGA values in case of constant b-value.

Moderate seismic activity affects contemporary sediment yields

Current models aiming to simulate contemporary sediment yield (SY) implicitly assume that tectonic effects are either irrelevant or are reflected by catchment topography. In this study we analyse the relation between SY and seismic activity, a component of tectonic processes. Results show a spatial correlation between SY and seismic activity expressed as the estimated peak ground acceleration (PGA) with a 10% exceedance probability in 50 years. PGA has a significant impact on the spatial variation of SY, even after correcting for cross-correlations with topography, lithology or other factors that may influence SY. Based on three distinct data sets, we demonstrate that this effect is significant both for small catchments in Europe (0.3–3940 km2) and for large river systems worldwide (1580–6.15×106 km2) and that seismic activity may be even more important for explaining regional variation in SY than land use or many other commonly considered factors (e.g. catchment area, climate). We show that explicitly considering seismic activity may lead to SY-estimates that easily deviate a factor 2 or more compared to estimates that do not consider seismic activity. This is not only the case for highly seismically active regions: also in regions with a weak to moderate seismic regime seismic activity helps explaining regional patterns in SY. We argue that these findings have important implications for a better understanding of SY and its sensitivity to human impacts, as well as for our comprehension of sediment fluxes at longer timescales.

A review of strong motion studies in Gujarat State of western India

The present work reviews the strong motion studies done in Gujarat State of western India. Prior to the 2001 Bhuj earthquake, no strong motion instrument was in operation in Gujarat. After the earthquake, number of research institutes/universities from India and abroad deployed strong motion instruments to study aftershock activity, source dynamics, path and site effects. The strong motion recordings have enhanced the general understanding of the physics of earthquakes in the region. An attempt has been made to develop attenuation relationship for the Gujarat region from the actual ground motions recorded by the strong motion networks. The Government of Gujarat with the help from Asian Development Bank, World Bank (WB), Ministry of Science and Technology and Ministry of Earth Sciences, Government of India, has established a permanent dense network of strong motion accelerograph (SMA) all over Gujarat. In addition, the Institute of Seismological Research has been established in Gandhinagar, Gujarat, with the help of WB for carrying out seismological research. Recently, many important studies have been carried out using actual acceleration data obtained from a dense network of 54 SMA, as well as synthetic data generated using region-specific ground motion parameters. The recorded data are used to obtain region-specific ground motion parameters and ground motion prediction equation. A deterministic hazard analysis for the entire state of Gujarat has been carried out using site-specific ground motion parameters. The estimated peak ground acceleration and modified Mercalli intensity values have been used to estimate the vulnerability of the different types of buildings in 31 cities of Gujarat. As Gujarat has three distinct regions having varied geological conditions, the recorded strong motion data gave an opportunity to study the effect of geological and local-site conditions on the response spectra. This study for an intra-plate region like Gujarat is a pioneer work. Still, lots of research work need to be carried out as more and more data are available, such as development of more robust ground motion prediction equations and a 3D-velocity structure of Gujarat. Generation of shake maps in real time and a credible early earthquake warning system is need of the hour for disaster mitigation and management.

Use of seismic early warning information to calibrate variable dampers for structural control of a highway bridge: evaluation of the system robustness

The seismic events occurred in recent years highlighted the extreme vulnerability of large part of the existing constructed facilities and the need to adopt innovative solutions to improve their seismic performance. With this purpose, the possible exploitation of a seismic early warning system (SEWS) in the framework of semi-active structural control using magnetorheological (MR) dampers is herein investigated. The main idea consists in the use of these time-varying properties devices to control an hosting structure by changing their behaviour according to an anticipate estimate, provided by the SEWS, of the peak ground acceleration (PGA) of the incoming earthquake. In this way, the dampers are able to adapt their mechanical characteristics to the specific earthquake obtaining the optimal seismic response. The present paper describes the application of this protection technique to a case-study problem, a highway bridge located in Southern California. The seismic response of the benchmark bridge is investigated by nonlinear time-history analyses by adopting 16 real earthquake ground excitations. These accelerograms cover a wide variety of magnitudes, distances to fault and soil types. Possible errors on estimation of PGA provided by SEWS and their effects on the proposed control system are also considered. The results obtained confirm that unavoidable errors in the PGA estimates provided by the SEWS do not propagate to the seismic response. Conversely, the proposed strategy turns out to damp these errors, resulting in a robust seismic behaviour of the protected structure.

Rapid on-site peak ground acceleration estimation based on support vector regression and P-wave features in Taiwan

This study extracted some P-wave features from the first few seconds of vertical ground acceleration of a single station. These features include the predominant period, peak acceleration amplitude, peak velocity amplitude, peak displacement amplitude, cumulative absolute velocity and integral of the squared velocity. The support vector regression was employed to establish a regression model which can predict the peak ground acceleration according to these features. Some representative earthquake records of the Taiwan Strong Motion Instrumentation Program from 1992 to 2006 were used to train and validate the support vector regression model. Then the constructed model was tested using the whole earthquake records of the same period as well as the 2010 Kaohsiung earthquake with 6.4 ML. The effects on the performance of the regression models using different P-wave features and different length of time window to extract these features are studied. The results illustrated that, if the first 3s of the vertical ground acceleration was used, the standard deviation of the predicted peak ground acceleration error of the whole tested 15-years earthquake records is 20.89gal.The length of time window could be shortened, e.g. 1s, and the prediction error is slightly sacrificed, in order to prolong the lead-time before destructive S-waves reaches.

Influence of epicentral distance on local seismic response in Kolkata City, India

The influence of source and epicentral distance on the local seismic response in the Kolkata city is investigated by computing the seismic ground motion along 2-D geological cross-sections in the Kolkata city for the earthquake that occurred on 12 June 1897 (M w = 8.1; focal mechanism: dip = 57°, strike = 110° and rake = 76°; focal depth = 9 km) in Shillong plateau. For the estimation of ground motion parameters, a hybrid technique is used, which is the combination of modal summation and finite difference method. This technique allows the estimation of site specific ground motion for various events located at different distances from Kolkata city, taking into account simultaneously the position and geometry of the seismic source, the mechanical properties of the propagation medium and the geotechnical properties of the site. The epicenter of the Shillong earthquake is about 460 km away from Kolkata. The estimated peak ground acceleration (PGA) varies in the range of 0.11–0.18 g and this range corresponds to the intensity of IX to X on the Mercalli-Cancani-Sieberg (MCS) scale and VIII on the Modified Mercalli (MM) scale. The maximum amplification in terms of response spectral ratio (RSR) varies from 10 to 12 in the frequency range 1.0–1.5 Hz. These amplifications occur in correspondence to low-velocity shallow, loose soil deposit. The comparison of these results with earlier ones obtained considering the Calcutta earthquake that occurred on 15 April 1964 (M w = 6.5; focal mechanism: dip = 32°, strike = 232° and rake = 56°; focal depth = 36 km) shows that the source parameters (magnitude and focal mechanism) and epicentral distance play an important role on site response but the variation in the frequency of the peak values (RSR) is negligible. The obtained results match with observed reported intensities in Kolkata region.

Seismic Design Value Evaluation Based on Checking Records and Site Geological Conditions Using Artificial Neural Networks

This study proposes an improved computational neural network model that uses three seismic parameters (i.e., local magnitude, epicentral distance, and epicenter depth) and two geological conditions (i.e., shear wave velocity and standard penetration test value) as the inputs for predicting peak ground acceleration—the key element for evaluating earthquake response. Initial comparison results show that a neural network model with three neurons in the hidden layer can achieve relatively better performance based on the evaluation index of correlation coefficient or mean square error. This study further develops a new weight-based neural network model for estimating peak ground acceleration at unchecked sites. Four locations identified to have higher estimated peak ground accelerations than that of the seismic design value in the 24 subdivision zones are investigated in Taiwan. Finally, this study develops a new equation for the relationship of horizontal peak ground acceleration and focal distance by the curve fitting method. This equation represents seismic characteristics in Taiwan region more reliably and reasonably. The results of this study provide an insight into this type of nonlinear problem, and the proposed method may be applicable to other areas of interest around the world.

Estimation of Peak Ground Acceleration from Horizontal Rigid Body Displacement: A Case Study in Port-au-Prince, Haiti

The M 7.0 Haiti earthquake of 12 January 2010 caused catastrophic da- mage and loss of life in the capital city of Port-au-Prince. The extent of the damage was primarily due to poor construction and high population density. The earthquake was recorded by only a single seismic instrument within Haiti, an educational seis- mometer that was neither bolted to the ground nor able to record strong motion on scale. The severity of near-field mainshock ground motions, in Port-au-Prince and elsewhere, has thus remained unclear. We present a detailed, quantitative analysis of the marks left on a tile floor by an industrial battery rack that was displaced by the earthquake in the Canape Vert neighborhood in the southern Port-au-Prince metropolitan region. Results of this analysis, based on a recently developed formula- tion for predicted rigid body displacement caused by sinusoidal ground acceleration, indicate that mainshock shaking at Canape Vert was approximately 0:5g, correspond- ing to a modified Mercalli intensity of VIII. Combining this result with the weak- motion amplification factor estimated from aftershock recordings at the site as well as a general assessment of macroseismic effects, we estimate the peak acceleration to be ≈0:2g for sites in central Port-au-Prince that experienced relatively moderate damage and where estimated weak-motion site amplification is lower than that at the Canape Vert site. We also analyze a second case of documented rigid body dis- placement, at a location less than 2 km from the Canape Vert site, and estimate the peak acceleration to be approximately 0:4g at this location. Our results illustrate how observations of rigid body horizontal displacement during earthquakes can be used to estimate peak ground acceleration in the absence of instrumental data.

A method for spatial estimation of peak ground acceleration in dense arrays

SUMMARY A methodology for the interpolation of peak ground acceleration (PGA) from discrete array stations is developed. Limited number of accelerometers or difficulty of monitoring at unreachable locations often has a negative impact on the generation of the maps of shaking after an earthquake. In locations with no recordings, PGA is inferred from interpolation of recorded PGA. The presented methodology estimates PGA at an arbitrary set of closely spaced points, in a way that is statistically compatible with known or prescribed PGA at other locations. The observed data recorded by strong motion stations of Istanbul Earthquake Rapid Response System are used for the development and validation of the new numerical method. The estimated and recorded PGAs are compared. Biased ground motion prediction equations are also considered at the comparisons. Ground motion prediction equations underestimated both observed and estimated PGAs. It has been found that the methodology is very effective for highly vulnerable mega-cities and urban areas.

Strong-Motion Data from Structural Response Recorders in Indian Earthquakes

In the 1960s several hundred structural response recorders (SRR) were installed all over India. An SRR is a simple instrument consisting of six seismoscopes that provide “maximum response” during an earthquake, without providing the time history. In the past earthquakes, these SRRs have provided several hundred records but they have not been effectively utilized for hazard studies because the measurements from these instruments are considered crude. This paper compares the data obtained from SRRs with that from more modern strong-motion accelerographs (SMAs) for four earthquakes in India. It is shown through statistical analysis that the response obtained from the SRRs is comparable to that from the SMAs. A method has been presented for estimating peak ground acceleration (PGA) from SRR data. Thus, it is shown that SRRs can provide a substantial amount of PGA data for attenuation studies. Many countries may find SRRs useful because of the low costs associated with their manufacture and maintenance.

Robust attenuation relations for peak time-domain parameters of strong ground motions

This study presents new attenuation models for the estimation of peak ground acceleration (PGA), peak ground velocity (PGV), and peak ground displacement (PGD) using a hybrid method coupling genetic programming and simulated annealing, called GP/SA. The PGA, PGV, and PGD were formulated in terms of earthquake magnitude, earthquake source to site distance, average shear-wave velocity, and faulting mechanisms. A worldwide database of strong ground motions released by Pacific Earthquake Engineering Research Center (PEER) was employed to establish the models. A traditional genetic programming analysis was performed to benchmark the proposed models. For more validity verification, the GP/SA models were employed to predict the ground-motion parameters of the Iranian plateau earthquakes. Sensitivity and parametric analyses were carried out and discussed. The results show that the GP/SA attenuation models can offer precise and efficient solutions for the prediction of estimates of the peak time-domain characteristics of strong ground motions. The performance of the proposed models is better than or comparable with the attenuation relationships found in the literature.

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.