Vertical Peak Ground Acceleration Research Articles

The effect of the vertical excitation on horizontal response of structures

It is usual in design and assessment of structures to isolate the effects of vertical and horizontal excitations by ignoring their coupling effects. In this situation, total structural response is obtained by employing the well-known combination rules whereby independent assumed response components of earthquakes are combined. In fact, the effects of the simultaneity of the ground motion components are ignored. In this paper, the effect of vertical excitation on horizontal response of structures, the coupling of vertical and horizontal responses, has been evaluated. A computer program is prepared to perform nonlinear dynamic analysis based on the derived governing equations of coupled motions. In the case of simultaneous excitation the results show significant increases in spectral displacement in some periods of vibration in comparison to only horizontally excited systems. Moreover, whenever ratio of the vertical peak ground acceleration to horizontal one become larger, the significant increase in horizontal spectral displacements are observed.

Prediction of ground motion parameters for the volcanic area of Mount Etna

Ground motion prediction equations (GMPEs) have been derived for peak ground acceleration (PGA), velocity (PGV), and 5 % damped spectral acceleration (PSA) at frequencies between 0.1 and 10 Hz for the volcanic area of Mt. Etna. The dataset consists of 91 earthquakes with epicentral distances between 0.5 and 100 km. Given the specific characteristics of the area, we divided our data set into two groups: shallow events (SE, focal depth 5 km). The range of magnitude covered by the SE and the DE is 3.0 ≤ M L ≤ 4.3 and 3.0 ≤ M L ≤ 4.8, respectively. Signals of DE typically have more high frequencies than those of SE. These differences are clearly reflected in the empirical GMPEs of the two event groups. Empirical GMPEs were estimated considering several functional forms: Sabetta and Pugliese (Bull Seism Soc Am 77:1491–1513, 1987) (SP87), Ambraseys et al. (Earth Eng Struct Dyn 25:371–400, 1996) (AMB96), and Boore and Atkinson (Earth Spectra 24:99–138, 2008) (BA2008). From ANOVA, we learn that most of the errors in our GMPEs can be attributed to unmodeled site effects, whereas errors related to event parameters are limited. For DE, BA2008 outperforms the simpler models SP87 or AMB96. For SE, the simple SP87 is preferable considering the Bayesian Information Criterion since it proves more stable with respect to confidence and gives very similar or even lower prediction errors during cross-validation than the BA2008 model. We compared our results to relationships derived for Italy (ITA10, Bindi et al. Bull Earth Eng 99:2471–2488, 2011). For SE, the main differences are observed for distances greater than about 5 km for both horizontal and vertical PGAs. Conversely, for DE the ITA10 heavily overestimates the peak ground parameters for short distances.

Preliminary Evaluation of Ground Motions from Earthquakes in Alberta

Between 9 September 2013 and 22 January 2015, more than 900 seismic events in local magnitude ( M L) range 1–4 were detected and located in near‐real time by the new TransAlta/Nanometrics network in western Alberta, which commenced operation in the fall of 2013. The network comprises 27 three‐component broadband seismograph stations, located as shown in Figure 1, which act in cooperation with other real‐time seismograph stations operated by the Alberta Geological Survey (AGS) (Stern et al. , 2011) and the Geological Survey of Canada (GSC). There are additional campaign‐mode stations in the Canadian Rockies and Alberta Network (CRANE) network operated by the University of Alberta (Gu et al. , 2011). Figure 1. Locations of stations and study events in Alberta. Events that are considered to be blasts are designated by an x within the magnitude symbol. Note that the deformation front that marks the boundary of the Rocky Mountains is distinguishable by topography. In this study, we compile and analyze a ground‐motion database of 5% damped pseudospectral acceleration (PSA) from the signals recorded on the TransAlta/Nanometrics stations in order to gain an initial understanding of overall ground‐motion source, attenuation, and site characteristics in the region. A catalog of events is provided on www.inducedseismicity.ca (last accessed May 2015); the locations and initial magnitudes of events were obtained by Nanometrics (www.nanometrics.ca; last accessed May 2015). We processed the recorded time series as described in Assatourians and Atkinson (2010). Briefly, the velocity time series are corrected for glitches and trends, then filtered and corrected for instrument response in the frequency domain. Differentiation to generate acceleration time series is done in the frequency domain before conversion back to the time domain. Horizontal and vertical peak ground velocity and peak ground acceleration values are computed from peak amplitudes of instrument‐corrected time series, and 5% damped …

Effects of 2D small-scale sedimentary basins on strong ground motion characteristics

A lot of research on the 2D or 3D effects of large-scale basins (within several kilometers depth) have been conducted in the past. However, different 2D aspects of small-scale sedimentary basins (within tens of meters depth) remain in the developing stage. Here, an attempt is made to analyze different aspects of small-scale basins using both numerical and empirical investigations. In the first step, the 2D effects of small-scale basins on strong motion characteristics are numerically examined both in the time and frequency domains. In addition, the effects of input motion are also explained by the results of model excitation in different orthogonal directions. Then, the numerical outcomes are verified by the analysis of actual earthquake data recorded at a downhole array in the Fujisawa small basin, Japan. In the second step, since available recorded earthquake data in small basins with a clear understanding of subsurface geology are very limited, different 2D aspects of the small basin are parametrically investigated. For this purpose, extensive parametrical studies are carried out on the main features of a small basin such as slope angle, shape, infill soil properties, and basin thickness by using the finite difference numerical method. The horizontal and vertical peak ground accelerations of 2D with respect to 1D ones are defined as the horizontal and vertical aggravation factors (AGH and AGV). The AGH and AGV factors show large sensitivity to infill soil properties, shape and thickness, and small sensitivity to slope angle. The values of AGH and AGV factors vary in the range of 0.5?2 with large variations around small basin edges due to wave coupling, conversion, scattering and focusing in the vicinity of small basin edges. These cause a complicated pattern of 2D de-amplification and amplification, which mostly affect the motion in the high frequency range (>1?Hz). Finally, the outcomes provide numerical and field evidence on the 2D effects of small basins, and give some recommendations for design codes.

Seismic Monitoring of a Slope to Investigate Topographic Amplification

Some earthquakes with a magnitude lower than Ms 7.0, such as Ludian earthquake in Yunnan in 2013, have triggered strong secondary geo-hazards in the form of slope failures. Topographic amplification is generally considered to be the main causal factor for these slope failures. However, until recently, this idea is not supported by appropriate seismic monitoring data. The Kangding Ms 6.3 earthquake on November 22 nd , 2014 was monitored in Lengzhuguan, Sichuan Province, located 56 km from the earthquake epicenter. Six monitoring instruments have recorded this earthquake. The horizontal and vertical component Peak Ground Acceleration (PGA), the site response directivity, the directional variation of the Arias intensity, and the acceleration response spectrum were determined from the data obtained. Conclusions could be drawn that the topographic amplification effect of the isolated ridge on the right bank was stronger than that of nearly linear slope on the left bank and the topographic amplification effect at a slope break was stronger than on a linear slope.

Density Distribution of Landslides Triggered by the 2008 Wenchuan Earthquake and their Relationships to Peak Ground Acceleration

The distribution of landslides induced by the 2008 M w 7.9 Wenchuan earthquake was investigated following the method of Meunier et al. (2007) to examine the relationships to peak ground acceleration (PGA). Results suggest that landslide densities are quantifiably related to PGA. Thresholds of PGAcr for landslide failure are ![Graphic][1] for average horizontal PGA and ![Graphic][2] for average vertical PGA. As with other earthquakes, the distribution of the Wenchuan earthquake‐triggered landslides can be described by two equations, based on area and source densities, respectively. The similar damping factors of ∼20 in these two equations suggest that both density distribution patterns of landslides reflect the dissipation of seismic energy. Landslide‐derived PGA equations were then produced for the hanging‐wall region of the earthquake‐affected area. The results indicate that it should be possible to produce an earthquake shake map from the distribution of earthquake‐triggered landslides in an area where there are few or no seismic instruments but many landslides. [1]: /embed/inline-graphic-1.gif [2]: /embed/inline-graphic-2.gif

Probabilistic and Deterministic Seismic Hazard Assessment: A Case Study in Babol

The risk of earthquake ground motion parameters in seismic design of structures and Vulnerability and risk assessment of these structures against earthquake damage are important. The damages caused by the earthquake engineering and seismology of the social and economic consequences are assessed. This paper determined seismic hazard analysis in Babol via deterministic and probabilistic methods. Deterministic and probabilistic methods seem to be practical tools for mutual control of results and to overcome the weakness of approach alone. In the deterministic approach, the strong-motion parameters are estimated for the maximum credible earthquake, assumed to occur at the closest possible distance from the site of interest, without considering the likelihood of its occurrence during a specified exposure period. On the other hand, the probabilistic approach integrates the effects of all earthquakes expected to occur at different locations during a specified life period, with the associated uncertainties and randomness taken into account. The calculated bedrock horizontal and vertical peak ground acceleration (PGA) for different years return period of the study area are presented.

Strong-Motion and Teleseismic Waveform Inversions for the Source Process of the 2003 Bam, Iran, Earthquake

The Bam earthquake ( M w 6.5) occurred on 26 December 2003 in southeastern Iran, causing a major disaster in the city of Bam. A remarkable vertical peak ground acceleration value of 988 cm/s2 and two horizontal pulses were recorded inside the damaged city. Previous analyses showed that the earthquake was caused by a subsurface rupture on an unknown strike‐slip fault. In this study, we attempt to determine the precise fault location and source process of the 2003 Bam earthquake by performing a multiple‐time‐window linear waveform inversion of teleseismic and strong‐motion data, both individually and jointly. We examined the general features of the fault location and the source process by analyzing the teleseismic displacement waveforms and determined the precise features and fault geometry by inverting the three components of strong‐motion velocity records. The final estimate of the source process of the 2003 Bam earthquake was determined by joint inversion of the datasets. Our results show that a single fault model, characterized by the appropriate location of the hypocenter, rake angle variations, and the Rayleigh‐like speed of the rupture front can satisfactorily explain the three components of the strong‐motion records at BAM station.

Study on Derailment Mechanism and Safety Operation Area of High-Speed Trains Under Earthquake

In order to investigate the derailment mechanism and safety operation area of high-speed trains under earthquake, a coupled vehicle-track dynamic model considering earthquake effect is developed, in which the vehicle is modeled as a 35 degrees of freedom (DOF) multibody system with nonlinear suspension characteristic and the slab track is modeled as a discrete elastic support model. The rails of the track are assumed to be Timoshenko beams supported by discrete rail fasteners, and the slabs are modeled with solid finite elements. The system motion equations are solved by means of an explicit integration method in time domain. The present work analyzes in detail the effect of earthquake characteristics on the dynamical behaviors of a vehicle-track coupling system and the transient derailment criteria. The considered derailment criteria include the ratio of the wheel/rail lateral force to the vertical force, the wheel loading reduction, the wheel/rail contact point traces on the wheel tread, and the wheel rise with respect to the rail top, respectively. The present work also finds the safety operation area, the derailment area, and the warning area of high-speed trains under earthquake, and their boundaries. These areas consist of three key parameters influencing the dynamical behavior of high-speed train and track under earthquake. The three key influencing parameters are, respectively, the vehicle speed and the lateral and vertical peak ground acceleration (PGA) of an earthquake. The results obtained indicate that the lateral earthquake motion has a greater influence on the vehicle dynamic behavior and its running safety compared to the vertical earthquake motion. The risk of derailment increases quickly with the increasing of lateral earthquake motion amplitude. The lateral earthquake motion is dominant in the vehicle running safety influenced by an earthquake. While the vertical earthquake motion promotes jumping of the wheels easily, not easy is flange climb derailment. And the effect of the vehicle speed is not significant under earthquake.

Near-Source Strong Ground Motion Characteristics of the 2008 Wenchuan Earthquake

The free-field strong ground motions recorded at 64 sites within 200 km from the ruptured Longmen Shan fault during the 12 May 2008 M w 7.9 Wenchuan earthquake were used to examine the near-source strong ground motioncharacteristics. The magnitude of vertical and horizontal peak ground accelerations (PGAs), frequency content, and duration of acceleration histories are analyzed. The observed peak ground accelerations at distances exceeding 60 km from the ruptured fault were significantly higher than those predicted by the Next Generation Attenuation (NGA) model, whereas, for periods of larger than 1 s, the spectral accelerations are much smaller than those of the NGA model. The same is also true for the observed peak ground velocities (PGVs). The duration of ground shaking is longer than for most earthquakes of comparable similar magnitude. For sites within 60 km from the ruptured fault, the accelerations observed on the hanging wall are larger than those observed on the footwall. The duration of ground shaking along the rupture direction (or the forward direction) is shorter than that opposite to the rupture direction (or the backward direction). There is also a systematic increase of PGA and PGV at sites located in the direction of the rupture propagation, whereas no such clear trend was found in the stations located along the backward direction. From the observed acceleration time histories at various locations, the rupture process of the 2008 Wenchuan appears to be more complicated than the focal mechanism interpreted from far-field seismic records. For example, the generation mechanism of the two distinct wave trains observed at Wolong and other stations need more detailed studies.

Ground-Motion Difference between Two Moderate-Size Intraplate Earthquakes in the United Kingdom

Two moderate-size earthquakes occurred in the United Kingdom, the first near Folkestone in 2007 with M w 4.0 and the second near Market Rasen in 2008 with M w 4.5. Both were strongly felt and caused some nonstructural damage. The earthquakes occurred at significantly different depths, the Folkestone earthquake at 5 km and the Market Rasen earthquake at 20 km. We determined the seismic moment and the stress drop of the two mainshocks, and two smaller earthquakes in the same locations, by modeling the source displacement spectra. We found stress drops of 30±34 bar and 344±136 bar for the Folkestone and Market Rasen mainshocks, respectively. This is a significant difference considering the earthquakes are only 275 km apart and both are of intraplate origin. We applied the stochastic ground-motion modeling technique and used the stress drop and seismic moment to compute vertical component peak ground acceleration. The modeled ground motions are consistent with the observations. We also computed vertical peak ground acceleration for a hypothetical M w 6.0 high stress-drop (200 bar) earthquake and found that it would be 4.6 m/sec2 at 20 km hypocentral distance.

Horizontal and vertical ground motion prediction equations derived from the Italian Accelerometric Archive (ITACA)

A set of Ground Motion Prediction Equations (GMPEs) for the Italian territory is proposed, exploiting a new strong-motion data set become available since July 2007 through the Italian Accelerometric Archive (ITACA). The data set is composed by 561 three-component waveforms from 107 earthquakes with moment magnitude in the range 4.0–6.9, occurred in Italy from 1972 to 2007 and recorded by 206 stations at distances up to 100 km. The functional form used to derive GMPEs in Italy (Sabetta and Pugliese in Bull Seismol Soc Am 86(2):337–352, 1996) has been modified introducing a quadratic term for magnitude and a magnitude-dependent geometrical spreading. The coefficients for the prediction of horizontal and vertical peak ground acceleration, peak ground velocity and 5% damped acceleration response spectra are evaluated. This paper illustrates the new data set, the regression analysis and the comparisons with recently derived GMPEs in Europe and in the Next Generation Attenuation of Ground Motions (NGA) Project.

Prediction of Vertical Peak Ground Acceleration and Vertical Acceleration Response Spectra from Shallow Crustal Earthquakes

Prediction of Vertical Peak Ground Acceleration and Vertical Acceleration Response Spectra from Shallow Crustal Earthquakes

Effect of Surface Geology on Ground Motions: The Case of Station TAP056 - Chutzuhu Site

In the Tatun mountain area of northern Taiwan are two strong motion stations approximately 2.5 km apart, TAP056 and TAP066 of the TSMIP network. The accelerometer at station TAP056 is often triggered by earthquakes, but that at TAP066 station is not. Comparisons of vertical and horizontal peak ground accelerations reveal PGA in the vertical, east-west, and north-south components at TAP056 station to be 3.89, 7.57, and 5.45 times those at station TAP066, respectively. The PGA ratio does not seem to be related to earthquake source or path. Fourier spectra of earthquake records at station TAP056 always have approximately the same dominant frequency; however, those at station TAP066 are different due to different sources and paths of different events. This shows that spectra at TAP056 station are mainly controlled by local site effects. The spectral ratios of TAP056/TAP066 show the S-wave is amplified at around 8~10 Hz. The horizontal/vertical spectral ratios of station TAP056 also show a dominant frequency at about 6 and 8~10 Hz. After dense microtremor surveying and the addition of one accelerometer just 20 meters away from the original observation station, we can confirm that the top soft soil layer upon which the observation station is constructed generates the local site response at station TAP056.

Estimation of peak ground accelerations for Mexican subduction zone earthquakes using neural networks


 
 
 An extensive analysis of the strong ground motion Mexican data base was conducted using Soft Computing (SC) techniques. A Neural Network NN is used to estimate both orthogonal components of the horizontal (PGAh) and vertical (PGAv) peak ground accelerations measured at rock sites during Mexican subduction zone earthquakes. The work discusses the development, training, and testing of this neural model. Attenuation phenomenon was characterized in terms of magnitude, epicentral distance and focal depth. Neural approximators were used instead of traditional regression techniques due to their flexibility to deal with uncertainty and noise. NN predictions follow closely measured responses exhibiting forecasting capabilities better than those of most established attenuation relations for the Mexican subduction zone. Assessment of the NN, was also applied to subduction zones in Japan and North America. For the database used in this paper the NN and the-better-fitted- regression approach residuals are compared.
 
 

Attenuation Relationships of Peak Ground Acceleration and Velocity for Crustal Earthquakes in Taiwan

Strong seismic ground-motion data obtained by the Taiwan Strong Motion Instrumentation Program (tsmip) and Central Mountain Strong Motion Array (cmsma) are used to derive new attenuation relationships for the vertical and horizontal peak ground acceleration (pga) and peak ground velocity (pgv) for crustal earthquakes in Taiwan. More than 7900 three-component accelerograms recorded from 51 crustal earthquakes in Taiwan, with M w magnitudes ranging from 4.0 to 7.1, have been analyzed to study the dependence of peak ground motion parameters on magnitude, distance, regional and local site effects, through attenuation relationships. We first found that, for both pga and pgv, the attenuation relationships decay faster with distance for the vertical component than for the horizontal component. Also, the attenuation relationships decay faster with distance for the vertical pga than for the vertical pgv. We further compared the attenuation relationships for three subregions (chy, iwa, and nto) and the whole Taiwan region (twn). It is found that the chy area has higher ground motion, either in pga or pgv, than the other areas, especially at near-source distances. This is because the chy area is located on a thick, recent alluvial plain. Comparison of our new attenuation relationships with strong-motion data from the 1999 Chi-Chi earthquake ( M w 7.7) and the 2003 Cheng-Kung earthquake ( M w 6.8) shows that the attenuation relationships developed for M w ≤7 can be extrapolated to make reasonable estimates of strong motion from larger M w ≥7 earthquakes. Finally, we analyzed the residuals to investigate variations of pga and pgv with respect to site conditions. The results show that (1) the residual contour maps, especially for the pgv, have high consistency with the regional geology and topography of Taiwan. (2) The pgv residual contours reveal that Taipei Basin, Changhua Plain, Chianan Plain, Pingtung Valley, Ilan Plain, and Taitung Longitudinal Valley have high residual values. Note that most major metropolitan areas all fall in high residual areas. (3) The site classification based on geologic criteria by Lee et al. (2001) can be simplified into three classes, that is, class E for soft soils, a combination of classes C and D for dense and stiff soils, and class B for rocks. These three site classes are mostly distributed, respectively, in the alluvial plains at an elevation less than 50 m, in terraces and hills at an elevation less than 1000 m, and in high mountainous areas.

Empirical Ground-Motion Attenuation Relations for the Eastern Alps in the Magnitude Range 2.5-6.3

In this paper we use a large data set of seismometric and accelerometric recordings (3168 vertical and 1402 for each of the horizontal components) collected by various networks in the eastern Alps to estimate empirical ground-motion attenuation relations valid in the magnitude range 2.5–6.3 for distances of up to 130 km. Relations are developed for horizontal and vertical peak ground acceleration and velocity, Arias intensity, response spectral acceleration, and Fourier amplitude for 46 periods between 0.1 and 2 sec. We adopt a simple magnitude-dependent attenuation model predicting closer attenuation curves and decreasing distance attenuation for increasing magnitude. We use truncated regression analysis to deal with the problem of non-triggering stations; with respect to other approaches, our solution does not require any discarding of data or the knowledge of which stations did not trigger. Our relations agree with others suitable for the study region for magnitudes greater than 5.8, while they have a faster attenuation for lower magnitudes. In an attempt to reduce the standard deviation, we have introduced soil classification into the relation, as well as a characterization of sites by means of H/V ratios. These ratios were estimated either by earthquakes (receiver function) or by the background seismic noise (Nakamura’s ratios). Similar to findings in other studies, the improvement obtained with soil classification is negligible, while H/V ratios reduce the standard deviation by up to 22%. Finally, we have investigated the implications of these new relations for seismic hazard assessment considering two sites of interest located in northeastern Italy (Udine and Gemona). In both cases, the difference in the hazard estimates for return periods shorter than 100 years is notable with respect to all other available relations.

Equations for the Estimation of Strong Ground Motions from Shallow Crustal Earthquakes Using Data from Europe and the Middle East: Vertical Peak Ground Acceleration and Spectral Acceleration

This article presents equations for the estimation of vertical strong ground motions caused by shallow crustal earthquakes with magnitudes M w 5 and distance to the surface projection of the fault less than 100km. These equations were derived by weighted regression analysis, used to remove observed magnitude-dependent variance, on a set of 595 strong-motion records recorded in Europe and the Middle East. Coefficients are included to model the effect of local site effects and faulting mechanism on the observed ground motions. The equations include coefficients to model the observed magnitude-dependent decay rate. The main findings of this study are that: short-period ground motions from small and moderate magnitude earthquakes decay faster than the commonly assumed 1/r, the average effect of differing faulting mechanisms is similar to that observed for horizontal motions and is not large and corresponds to factors between 0.7 (normal and odd) and 1.4 (thrust) with respect to strike-slip motions and that the average long-period amplification caused by soft soil deposits is about 2.1 over those on rock sites.

Building collapse and human deaths resulting from the Chi-Chi Earthquake in Taiwan, September 1999.

In this study, the authors attempted to determine factors associated with earthquake deaths in the great Chi-Chi Earthquake that occurred on September 21, 1999, in Taiwan. An isoseismal map was used to identify life-threatening hazards. The vertical peak ground acceleration of ground motion intensity was deemed the most appropriate index for the evaluation of building collapse and mortality. Mortality increased with the increase in earthquake intensity, and building collapse, approaching the epicenter. The greatest number of collapsed buildings and human deaths occurred between the Chelungpu Fault and the Shuantun Fault. Individuals 65 yr of age and older were the most vulnerable to the impact. The authors' findings suggest that improvements in earthquake-resistant building design and construction, as well as improved medical rescue for the elderly, could reduce the level of exposure to earthquake hazards.

Pseudostatic analysis of Tsao-Ling rockslide caused by Chi-Chi earthquake

During the 1999 Chi-Chi earthquake, extensive slope failures were triggered by the earthquake in central Taiwan. Among those, a large-scale dip-slope slide in Tsao-Ling occurred, which involved the mass movement of 120 million cubic meters. Four catastrophic dip-slope rockslide events in history in Tsao-Ling are reported; furthermore, the stability analysis of the Tsao-Ling landslide caused by the Chi-Chi earthquake was conducted for the original and remaining slope. Results of pseudostatic analysis indicated that a reduction factor of 2/3 for both vertical and horizontal peak ground acceleration with 30% of material strength degradation were likely the case for inducing the Tsao-Ling landslide, and the effects of vertical acceleration were significant. Accordingly, it was concluded that ground motion and degradation of material strength were the major factors for the inducement of the Tsao-Ling landslide by the Chi-Chi earthquake.