Peak Ground Velocity Values Research Articles

3D Nonlinear Ground‐Motion Simulation Using a Physics‐Based Method for the Kinburn Basin

AbstractWe used a finite‐difference modeling method, developed by Olsen–Day–Cui, to simulate nonlinear‐viscoelastic basin effects in a spectral frequency range of 0.1–1 Hz in the Kinburn bedrock topographic basin, Ottawa, Canada, for large earthquakes. The geotechnical and geological features of the study area are unique: loose, postglacial sediments with very low shear‐wave velocities (<200 m/s) overlying very firm bedrock with high shear‐wave velocities (>2000 m/s). Comparing records and simulated velocity time series showed regular viscoelastic simulations could model the ground motions at the rock and soil sites in the Kinburn basin for the Ladysmith earthquake, a local earthquake occurred on 17 May 2013 with Mw 4.7 (MN 5.2). The Ladysmith earthquake was scaled to provide a strong level of shaking for investigating the nonlinear behavior of soil; therefore, a new nonlinear‐viscoelastic subroutine was introduced to the program. A modeled stress–strain relationship associated with ground‐motion modeling in the Kinburn basin using a scaled Ladysmith earthquake event of Mw 7.5 followed Masing’s rules. Using nonlinear‐viscoelastic ground‐motion simulations significantly reduced the amplitude of the horizontal component of the Fourier spectrum at low frequencies and the predicted peak ground acceleration and peak ground velocity values compared with regular linear viscoelastic simulations; hence, the lower soil amplification of seismic waves and the frequency and amplitude spectral content were altered by the nonlinear soil behavior. In addition, using a finite‐fault model to simulate an earthquake with Mw 7.5 was necessary to predict the higher levels of stresses and strains, which were generated in the basin. Using a finite‐fault source for the nonlinear‐viscoelastic simulation caused decreases in the horizontal components because of the shear modulus reduction and increase of damping.

The Effect of Fault Geometry and Minimum Shear Wavespeed on 3D Ground-Motion Simulations for an Mw 6.5 Hayward Fault Scenario Earthquake, San Francisco Bay Area, Northern California

AbstractWe investigated the effects of fault geometry and assumed minimum shear wavespeed (VSmin) on 3D ground-motion simulations (0–2.5 Hz) in general, using a moment magnitude (Mw) 6.5 earthquake on the Hayward fault (HF). Simulations of large earthquakes on the northeast-dipping HF using the U.S. Geological Survey (USGS) 3D seismic model have shown intensity asymmetry with stronger shaking for the Great Valley Sequence east of the HF (hanging wall) relative to the Franciscan Complex to the west (footwall). We performed simulations with three fault geometries in both plane-layered (1D) and 3D models. Results show that the nonvertical fault geometries result in larger motions on the hanging wall relative to the vertical fault for the same Earth model with up to 50% amplifications in single-component peak ground velocity (PGV) within 10 km of the rupture. Near-fault motions on the footwall are reduced for the nonvertical faults, but less than they are increased on the hanging wall. Simulations assuming VSmin values of 500 and 250 m/s reveal that PGVs are on average 25% higher west of the HF when using the lower VSmin, with some locations amplified by a factor of 3. Increasing frequency content from 2.5 to 5 Hz increases PGV values. Spectral ratios of these two VSmin cases show average amplifications of 2–4 (0.5–1.5 Hz) for the lower VSmin west of the fault. Large differences (up to 2×) in PGV across the HF from previous studies persist even for the case with a vertical fault or VSmin of 250 m/s. We conclude that assuming a VSmin of 500 m/s underestimates intensities west of the HF for frequencies above 0.5 Hz, and that low upper crustal (depth <10 km) shear wavespeeds defined in the 3D model contribute most to higher intensities east of the HF.

Qualitative Method and Case Study for Ground Vibration of Tunnels Induced by Fault-Slip in Underground Mine

To evaluate tunnel ground vibrations induced by fault-slip in underground mine, it is crucial to resolve the peak ground velocity (PGV) and the peak ground acceleration (PGA). To quantify PGV and PGA in three-dimensional space, the forces acting on the fault and the seismic wave radiation pattern were investigated. A qualitative method for ground vibration of tunnels induced by fault-slip in underground mine was proposed and applied to the Yongshaba Phosphate Mine, China. Firstly, the moment tensor of the significant fault-slip event was obtained using a full waveform source inversion method based on the recorded seismograms. It describes the forces acting on the fault and the seismic wave radiation pattern. Then, the inverted source was used as a reference to evaluate the ground vibrations under possible larger seismic magnitudes and probable slip models. The vibrations along the tunnels resulted from different slip models were calculated using the representation theorem by the convolution of the Green’s function and the corresponding moment tensor. The velocity series and the acceleration series were obtained. Results show that the spatial distribution of the ground motions are closely related to sensor-source distance, the sensor-source azimuth, as well as the strike, dip, and rake configuration of the slip model. The seismic magnitude has an exponential effect on the distribution of the PGVs and PGAs. The PGV and PGA have similar spatial distribution patterns. The PGV values of the north and vertical components show nearly 5 times higher than the east component. The vertical vibrations affect the widest area. The ground support principles were suggested considering the parameters including the PGVs, the PGAs, the rock mass rating, and the dynamic loads.

Estimation of maximum mass velocity from macroseismic data: A new method and application to archeoseismological data

An important task in seismic hazard assessment is the estimation of intensity and frequency of rare strong seismic shaking, in particular, the long-term peak ground velocity values (PGVs). A recently proposed method is suitable for simply estimating PGVs based on the examination of the magnitude of displacements of rock blocks. The effectiveness of this method is demonstrated by results of studies on the source zones of two large earthquakes and a vicinity of one strong explosion. In this study, the method is applied to the examination of archeoseismological data from the ancient Rehovot-ba-Negev city and other ancient cities from the Negev desert (in Southern Israel) where numerous evidences of presumable seismic damage were found earlier. The cities and also a sophisticated irrigation system within the region, which existed in the Negev desert, were abandoned however in the middle of the seventh century. The abandonment could be caused by a combined effect, from not only the cessation of the state support from Byzantium as a result of the Arab conquest but also the severe destruction from the strong earthquake that hit the area at that time. The intensities of the seismic events that hit the cities were estimated earlier, which are within the range of 8–9. Our estimates indicate that the PGV values are about 1.5 m/s. Hence, the magnitude of the causative earthquake could be in the range M ≈ 6.5–7.5, and the location of the epicenter might be at a distance of a few dozens of kilometers from the ancient Rehovot-ba-Negev city, while the other variants associated with the earthquake seem to be less probable.

AN INVESTIGATION ON THE ATTENUATION CHARACTERISTICS OF DISTANT GROUND MOTIONS IN PENINSULAR MALAYSIA BY COMPARING VALUES OF RECORDED WITH ESTIMATED PGA AND PGV

The development of a design motion requires some input on ground motion characteristics. For a country such as Malaysia, where historical data is lacking and seismic activities are low, the information on characteristics of ground motion may be obtained by utilizing established attenuation relationships. This study aims to investigate the characteristics of distant ground motions in Peninsular Malaysia, which originated from the active tectonic plate of Sumatra, by comparing recorded peak ground acceleration (PGA) and peak ground velocity (PGV) values with those estimated using four attenuation models. Selected attenuation models are the Atkinson and Boore (1995), the Toro et al. (1997), the Dahle et al. (1990), and the Si and Midorikawa (1999) models. The analysis for comparison was made by employing a maximum of 46 horizontal component accelerograms, recorded at 14 seismic stations. These are data derived from 15 interplate earthquakes between May 2004 and July 2007. Recorded PGA and PGV values were plotted on respective attenuation curves to examine ground motion attenuation characteristics. Results indicated that attenuation models, established for stable tectonic regions, provide good estimation of PGA and PGV for Sumatran earthquakes for magnitude range of 5.9 to 9.0. The study shows that the Dahle et al. (1990) model best represents the characteristics of ground motions in terms of PGA, while the Atkinson and Boore (1995) model gives appropriately estimate ground motions in terms of PGV

The 1895 Ljubljana earthquake: can the intensity data points discriminate which one of the nearby faults was the causative one?

The earthquake (Mw 6 from the SHEEC defined by the MDPs) that occurred in the central part of Slovenia on 14 April, 1895, affected a broad region, causing deaths, injuries, and destruction. This event was much studied but not fully explained; in particular, its causative source model is still debated. The aim of this work is to contribute to the identification of the seismogenic source of this destructive event, calculating peak ground velocity values through the use of different ground motion prediction equations (GMPEs) and computing a series of ground motion scenarios based on the result of an inversion work proposed by Jukić in 2009 and on various fault models in the surroundings of Ljubljana: Vič, Želimlje, Borovnica, Vodice, Ortnek, Mišjedolski, and Dobrepolje faults. The synthetic seismograms, at the basis of our computations, are calculated using the multi-modal summation technique and a kinematic approach for extended sources, with a maximum peak ground velocity value of 1 Hz. The qualitative and quantitative comparison of these simulations with the macroseismic intensity database allows us to discriminate between various sources and configurations. The quantitative validation of the seismic source is done using ad hoc ground motion to intensity conversion equations (GMICEs), expressly calculated for this study. This study allows us to identify the most probable causative source model of this event, contributing to the improvement of the seismotectonic knowledge of this region. The candidate fault that has the lowest values of average differences between observed and calculated intensities and chi-squared is a strike slip fault with a toward-north rupture as the Ortnek fault.

Italian vs. worldwide history of largest PGA and PGV

Earthquake engineering and engineering seismology greatly rely on the information gathered from observed data. This is especially true when it comes to ground motion intensity measures, which are related to the damaging potential of earthquakes. Observed maxima of peak ground acceleration (PGA) and peak ground velocity (PGV) can provide reference values for hazard assessment, which often needs to extrapolate towards large return periods. This simple study attempts to reconstruct the history of the largest values of PGA and PGV observed in Italy since 1972. Results reveal that the current maxima of PGA and PGV values were recorded during the 2016 central Italy earthquake sequence. For comparison, up-to-date global trends of PGA and PGV maxima are also compiled, following relevant literature on the topic and investigating a number of international databases. It is found that these trends, which are roughly linear in logarithmic scale, correspond to the increase of ground motion records worldwide.

A Seismic Intensity Survey of the 1 April 2014 M 8.2 Iquique, Chile, Earthquake and Tsunami, and a Comparison with Strong‐Motion Data

ABSTRACT We conducted a regional seismic intensity survey in northern Chile following the 1 April 2014 M 8.2 Iquique earthquake to document the level of damage caused by the earthquake and tsunami. We observed very limited damage at the 204 sites surveyed. The modified Mercalli intensities (MMIs) reached a maximum value of VI adjacent to the earthquake rupture plane. The contours of our MMI map are similar in shape to the contour maps of peak ground acceleration (PGA) and peak ground velocity (PGV). A comparison of our seismic intensities with the recorded PGA and PGV values reveals that our MMI values are one to two units lower than predicted by ground‐motion intensity conversion equations (GMICEs). We propose that this is due to the well‐engineered buildings and moderate levels of high‐frequency (0.5–5 Hz) ground shaking experienced during this earthquake. Whether existing GMICEs consistently overpredict seismic intensities for large subduction‐zone earthquakes deserves further study.

Ground Motion Parameter Sensitivity to Shear Strain Ratio in Equivalent Linear Analyses

This paper compares 5,715 equivalent linear analyses to examine the sensitivity of the results to the shear strain ratio ( SR). The results show that as SR increases, equivalent linear analyses predict larger values of maximum shear strain ( γ max), peak ground displacement, mean period ( T m), and spectral acceleration ( Sa) at long periods, smaller values of peak ground acceleration ( PGA), Arias intensity, significant duration, and Sa at short periods, and similar values of peak ground velocity and Sa at middle periods. SR has a non-negligible effect on predicted values of γ max, T m, and Sa at short and long periods. This study also compares measured values from 80 ground motions and six vertical arrays with the results of equivalent linear analyses conducted using two methods to calculate SR. The results show that using SR = 0.65 gives a 2–10% better fit than using SR = ( M − 1)/10, where M is the earthquake magnitude.

Comparison of Equivalent Linear and Nonlinear Site Response Analysis Results and Model to Estimate Maximum Shear Strain

We compared the results of equivalent linear (ELA) and nonlinear site response analyses (NLA) and found that the differences between the values of the peak ground acceleration ( PGA), peak ground velocity ( PGV), Arias intensity ( I a), significant duration ( D5–75), and response spectrum for periods between 0.025 s and 2 s predicted by each method are non-negligible for maximum shear strain values predicted by ELA ( γ max, ELA) greater than 0.04% to 1.0%. As γ max, ELA increases, ELA in general predict smaller shear strain and D5–75 values, and larger PGA, PGV, I a, mean period, and response spectral values for periods less than 0.1 s and periods near the natural site period than NLA. To help researchers and practitioners decide when to use ELA and/or NLA, we developed a model to estimate γ max, ELA before conducting a site response analysis.

Strong ground motion in the Kathmandu Valley during the 2015 Gorkha, Nepal, earthquake

On 25 April 2015, a large earthquake of Mw 7.8 occurred along the Main Himalayan Thrust fault in central Nepal. It was caused by a collision of the Indian Plate beneath the Eurasian Plate. The epicenter was near the Gorkha region, 80 km northwest of Kathmandu, and the rupture propagated toward east from the epicentral region passing through the sediment-filled Kathmandu Valley. This event resulted in over 8000 fatalities, mostly in Kathmandu and the adjacent districts. We succeeded in observing strong ground motions at our four observation sites (one rock site and three sedimentary sites) in the Kathmandu Valley during this devastating earthquake. While the observed peak ground acceleration values were smaller than the predicted ones that were derived from the use of a ground motion prediction equation, the observed peak ground velocity values were slightly larger than the predicted ones. The ground velocities observed at the rock site (KTP) showed a simple velocity pulse, resulting in monotonic-step displacements associated with the permanent tectonic offset. The vertical ground velocities observed at the sedimentary sites had the same pulse motions that were observed at the rock site. In contrast, the horizontal ground velocities as well as accelerations observed at three sedimentary sites showed long duration with conspicuous long-period oscillations, due to the valley response. The horizontal valley response was characterized by large amplification (about 10) and prolonged oscillations. However, the predominant period and envelope shape of their oscillations differed from site to site, indicating a complicated basin structure. Finally, on the basis of the velocity response spectra, we show that the horizontal long-period oscillations on the sedimentary sites had enough destructive power to damage high-rise buildings with natural periods of 3 to 5 s.

Generation of Fragility Curves for Typical RC Health Care Facilities: Emphasis on Hospitals in Turkey

AbstractThis study uses fragility curves to focus on the seismic safety evaluation of RC hospital buildings in Turkey. Three hospital buildings with varying heights of 3–5 stories are selected, and a set of fragility curves are generated for each class. The major parameters considered in this study are the number of stories, lateral stiffness, strength, and displacement capacities of the selected template designs. A large number of pushover and time history analyses are deployed under a set of 100 strong ground motion records. Fragility curves are generated based on the analysis results for each of the typical buildings. Peak ground velocity (PGV) is selected as the measure of seismic intensity. From the generated sets of the fragility curves, it is observed that damage probabilities are significantly affected by the concrete and detailing quality. Using the constructed fragility curves, collapse probabilities of existing public buildings were estimated according to PGV values. The estimated damage by fra...

Statistics of Ground Motions in a Foam Rubber Model of a Strike‐Slip Fault

Abstract The peak ground acceleration (PGA) and peak ground velocity (PGV) from 5058 ruptures of a foam rubber stick‐slip model are not distributed according to a lognormal probability distribution function. PGA and PGV values are decomposed using the method of Anderson and Uchiyama (2011). The statistically significant deviations from the lognormal distribution occur near the peak of the distribution. In some cases, high‐amplitude tails differ by a much greater ratio, but the statistical significance of this effect is low. This result is true of both raw data and data adjusted for site and magnitude. Event terms are also not lognormal but can be modeled as a sum of three or four lognormal subdistributions, which possibly represent different preferred rupture initiation points rather than a uniform distribution of initiation points. The event term subdistributions with highest median values have small standard deviations, so if shapes of this nature were used in ground‐motion prediction equations (GMPEs) during a probabilistic seismic‐hazard analysis, the effect of the long tail of the lognormal distribution in controlling the hazard would be weakened considerably. Static stress drop was recorded for each event, and event terms for PGA and PGV are well correlated with static stress drop. Unlike Next Generation Attenuation‐West 2 GMPEs, residual variances for the foam model are dominated by variability in the source slip function, rather than the path and site effects. This difference in the variance budget results from the way in which the source and site residuals are defined in this study; the source uncertainty includes variation in the rupture size (magnitude) and location, along with deviations in distance and path. We do not know if these results apply to earthquakes, but we do think tests of repeating stick‐slip events in a physical system are useful to expand the set of credible hypotheses regarding possible behavior modes of earthquake faults.

Seismic hazard assessment for Yanbu metropolitan area, western Saudi Arabia

The stochastic method is used to predict ground motions for Yanbu metropolitan area which has been affected byseveral earthquakeswiththe maximum magnitudeof6.8in 1121 AD. The stochastic method has been used for simulating the time domain history for the peak ground acceleration (PGA), peak ground velocity (PGV), and peak ground dis- placement (PGD) at Yanbu metropolitan area. In addition, the response spectra at 3, 5, and 10 % of the damped pseudo-spectral acceleration (PSA) have been calculated at Al-Majd Sporting Club, Al-Maktabah, and Al-Shate Secondary School sites within the Yanbu metropolitan area. The results show that the values of PGA range from 137 to 388 cm/s 2 , PGV values vary from 8.96to 25.5 cm/s, and PGD values range from 6.7 to 20.9 cm. The values of pseudo- spectral acceleration and predominant period are 974.53 cm/ s 2 (with 5 % damping) at 0.14 s for Al-Majd Sporting Club, 487.06cm/s 2 at 0.19s for Al-Maktabah site, and 700.83cm/s 2 at 0.14 s for Al-Shate Secondary School. It is cleared that the values of ground motion parameters are amplified due to the presence of thick sections of very soft to soft sediments to more than six times those of the hard rocks. Furthermore, the estimated predominant periods from this study are corre- lated well with that of multichannel analysis of surface wave (MASW) approach. These results should be taken into account during design and construction of civil engineering structures within the Yanbu metropolitan area.

A Refined Vs30 Map for Taiwan Based on Ground Motion Attenuation Relationships

Seismic hazard evaluations require an estimate of the expected ground motion at the site of interest usually by using attenuation relationships. The mean shear-wave velocity over the top 30 m (Vs30) is incorporated in the ground motion attenuation relationships in this study. By comparing the standard deviations of the residuals between the observed and predicted values before and after incorporating the site effect term Vs30, the reduction in standard deviation for the peak ground velocity (PGV) is significantly reduced by about 11%. Clearly, the refined attenuation relationships will be more useful for engineering purposes. Analyzing the site effect term using the amplification factor (relative to a site with Vs30 = 760 m s^(-1)), has revealed that the Changhua Plain, Chianan Plain, Pingtung Valley, Ilan Plain, and Taipei Basin have high values, implying large ground motion amplification. Following a disastrous earthquake, quick assessment and timely peak ground acceleration (PGA) and PGV map reporting will be critical for effective emergency response operations. After an earthquake we can combine the simple attenuation relationships, as determined from Model 1, to provide near real-time estimation and reporting of the PGA and PGV values for the Taiwan area. We can also use the relations between the intra-event site residual and the Vs30 to estimate the Vs30 for stations that have recorded strong motions, but do not yet have Vs30 information. Our approach including sites with estimated Vs30 has resulted in a refined Vs30 contour map that can be used for more realistic seismic hazard assessment for Taiwan. This approach is especially applicable to the foothill and mountain areas.

A Simple Model for Probabilistic Seismic Hazard Analysis of Induced Seismicity Associated with Deep Geothermal Systems

In the research project MAGS (Microseismic Activity of Geothermal Systems) a simple model was developed to determine seismic hazard as the annual frequency of the exceedance of ground motion of a certain size. Such estimates of the annual frequency of exceedance of prescriptive limits for the effects of vibrations on buildings and people are needed for the planning and licensing, but likewise for the development and operation of deep geothermal systems.For the development of the proposed model well established probabilistic seismic hazard analysis methods for the estimation of the hazard for the case of natural seismicity were adapted to the case of induced seismicity. Important differences between induced and natural seismicity had to be considered. These included significantly smaller magnitudes, depths and source to site distances of the seismic events. Hence, different ground motion prediction equations (GMPE) had to be incorporated to account for the seismic amplitude attenuation with distance, as well as for differences in the stationarity of the underlying tectonic and induced processes. Appropriate GMPEs in terms of peak ground velocity (PGV) were tested and selected from the literature. In the paper we present probabilistic seismic hazard analysis (PSHA) results for ground motion which can be linked to engineering regulations (e.g. German DIN 4150). It is thus possible to specify the probability of exceedance of prescriptive standard values and to decide (e.g. by the regulator responsible for commissioning) whether the annual number of exceedances for a site at a given level is acceptable or not. Additionally, hazard curves for induced and natural seismicity are compared to study the different impact at a site. Preliminary results for the circulation period (operation phase of the plant) at a geothermal site in Bavarian Molasse, Germany - for stiff soil, ignoring site effects - indicate higher frequencies of exceedance for induced seismicity than for natural seismicity only for low PGV values.

Magnitude Estimation for the 2011 Tohoku-Oki Earthquake Based on Ground Motion Prediction Equations

This study investigates whether real-time strong ground motion data from seismic stations could have been used to provide an accurate estimate of the magnitude of the 2011 Tohoku-Oki earthquake in Japan. Ultimately, such an estimate could be used as input data for a tsunami forecast and would lead to more robust earthquake and tsunami early warning. We collected the strong motion accelerograms recorded by borehole and free-field (surface) Kiban Kyoshin network stations that registered this mega-thrust earthquake in order to perform an off-line test to estimate the magnitude based on ground motion prediction equations (GMPEs). GMPEs for peak ground acceleration and peak ground velocity (PGV) from a previous study by Eshaghi et al. in the Bulletin of the Seismological Society of America 103. (2013) derived using events with moment magnitude (M) ≥ 5.0, 1998–2010, were used to estimate the magnitude of this event. We developed new GMPEs using a more complete database (1998–2011), which added only 1 year but approximately twice as much data to the initial catalog (including important large events), to improve the determination of attenuation parameters and magnitude scaling. These new GMPEs were used to estimate the magnitude of the Tohoku-Oki event. The estimates obtained were compared with real time magnitude estimates provided by the existing earthquake early warning system in Japan. Unlike the current operational magnitude estimation methods, our method did not saturate and can provide robust estimates of moment magnitude within ~100 s after earthquake onset for both catalogs. It was found that correcting for average shear-wave velocity in the uppermost 30 m ( $$ V_{{{\text{s}}_{30} }} $$ ) improved the accuracy of magnitude estimates from surface recordings, particularly for magnitude estimates of PGV (Mpgv). The new GMPEs also were used to estimate the magnitude of all earthquakes in the new catalog with at least 20 records. Results show that the magnitude estimate from PGV values using borehole recordings had the smallest standard deviation among the estimated magnitudes and produced more stable and robust magnitude estimates. This suggests that incorporating borehole strong ground-motion records immediately available after the occurrence of large earthquakes can provide robust and accurate magnitude estimation.

Using Borehole Records to Estimate Magnitude for Earthquake and Tsunami Early-Warning Systems

This paper presents a new application of the ground‐motion prediction equations (GMPEs) to estimate the event magnitude for earthquake and tsunami early warning systems. This technique incorporates borehole strong‐motion records along with surface recordings provided by Kiban Kyoshin network (KiK‐net) stations. We analyzed strong ground motion data from earthquakes with moment magnitude ( M ) ranging from 5.0 to 8.1 recorded by KiK‐net stations provided by Japan’s National Research Institute for Earth Science and Disaster Prevention (NIED) over the interval of 1998 to 2010. We used 2160 strong ground motion accelerograms with peak ground acceleration (PGA) larger than 10 cm/s2 recorded by borehole seismographs, and 890 waveforms with PGA larger than 80 cm/s2 recorded by surface seismographs to derive GMPEs for PGA and peak ground velocity (PGV) in Japan. These GMPEs are used as the basis for regional magnitude determination. Predicted magnitudes from PGA values (MPGA) and predicted magnitudes from PGV values (MPGV) were defined separately for borehole and surface recordings. MPGA and MPGV strongly correlate with the moment magnitude of the event, provided that at least 20 records for each event are available. The results show that MPGV from borehole data has the smallest standard deviation among the estimated magnitudes and provides an accurate early assessment of earthquake magnitude. We demonstrate that incorporation of borehole strong ground motion records immediately available after the occurrence of large earthquakes significantly increases the accuracy of earthquake magnitude estimation and improves earthquake and tsunami early warning systems performance.

Study on Instrumental Intensity Using Wenchuan Earthquake Records

This paper invesigates the peak ground acceleration (PGA) and peak ground velocity (PGV) regression equations as well as the PGA or PGV middle values in Chinese seismic intensity scale 2008 (the CSIS 2008), using the Wenchuan earthquake records of China with the full seismic information. Based on the analytical results, the PGA-V method is proposed to assess the instrumental intensity which combines both PGA and PGV. Besides, a problem is raised to further verify and modify the middle values of PGA or PGV for the seismic intensity VI and VII in the CSIS 2008.

Modelling basin effects on earthquake ground motion in the Santiago de Chile basin by a spectral element code

SUMMARY Simulations of strong ground motion within the Santiago de Chile Metropolitan area were carried out by means of 3-D deterministic wave propagation tool based on the spectral element method. The simulated events take into account the pronounced interface between the low-velocity sedimentary basin and the bedrock as well as topography of the area. To verify our model we simulated a regional earthquake recorded by a dense network installed in the city of Santiago for recording aftershock activity after the 2010 February 27 Maule main shock. The results proof the alluvial basin amplification effects and show a strong dependence of spectral amplification in the basin on the local site conditions. Moreover, we studied the seismic response due to a hypothetical Mw= 6.0 event occurring along the active San Ramon Fault, which is crossing the eastern edge of the city. The scenario earthquakes exhibit that an unfavourable interaction between fault rupture, radiation mechanism and complex geological and topographic conditions in the near-field region may give rise to large values of peak ground velocity in the basin. Finally, 3-D numerical predictions of ground motion are compared with the one computed according to ground motion prediction equations selected among the next generation attenuation relationships, in terms of ground motion peak values and spectral acceleration. The comparison underlines that the 3-D scenario simulations predict a significantly higher level of ground motion in the Santiago basin, especially over deep alluvial deposits. Moreover, also the location of the rupture nucleation largely influences the observed shaking pattern.