Strong Motion Network Research Articles

Probabilistic mechanics-based loss scenarios for school buildings in Basel (Switzerland)

Developing earthquake scenarios for cities in areas with a moderate seismicity is a challenge due to the limited amount of available data, which is a source of large uncertainties. This concerns both the seismic hazard, for which only recordings for small earthquakes are available and the unknown earthquake resistance of the majority of structures not designed for seismic loading. The goal of the present study is to develop coherent probabilistic mechanics-based scenarios for a mid-size building stock including a comprehensive analysis of the uncertainties. As an application, a loss assessment for the school buildings of the city of Basel is performed for different scenarios of historical significance, such as the 1356 event, and from the deaggregation of the Swiss Probabilistic Seismic Hazard Model of 2015. The hazard part of the computations (i.e. ground motion estimation) is based on this model, a regional microzonation and recordings of small earthquakes on a dense strong motion network to compute site-amplification factors. The school buildings, which are mainly unreinforced masonry or reinforced concrete shear wall buildings, have been classified according to a specifically developed taxonomy. Fragility curves have been developed using non-linear static procedures and subsequently, vulnerability curves in terms of human and financial losses are proposed. The computations have been run with the OpenQuake engine, carefully propagating all the recognized uncertainties. Scenarios before and after retrofitting measures show their impact on the earthquake safety. A sensitivity analysis shows that the largest uncertainties come from the ground motion prediction although an improvement of all parts of the model is necessary to decrease the uncertainties. Although improved data and models are still necessary to be developed, probabilistic mechanics-based models outperform the capabilities of deterministic and/or empirical models for retrieving realistic earthquake loss distributions.

Destructive near-fault strong ground motion from the 2016 Kumamoto prefecture, Japan, M7.3 earthquake

The sequence of the 2016 Kumamoto, Japan, earthquake, which included an initial M6.5 foreshock on April 14, followed by a larger M7.3 mainshock on April 16, and subsequently occurred high aftershock activity, caused significant damage in Kumamoto and neighboring regions. The near-field strong motion record by strong motion network (K-NET and KiK-net) and the intensity meter network demonstrated clearly the characteristics of the strong ground motion developed by the shallow (H = 12 km), inland earthquake comprising short-time duration ( 1G) ground accelerations. The velocity response spectra of the near-fault motion at Mashiki and Nishihara showed large levels (>300–550 cm/s) in the short-period range (T = 1–2 s), several times larger than that of the near-field record of the destructive 1995 Kobe earthquake (M7.3) and that of the 2004 Mid-Niigata earthquake (M6.8). This period corresponds to the collapse vulnerability of Japanese wooden-frame houses, and is the major cause of severe damage during the Kumamoto earthquake. The response spectra also showed extremely large levels (>240–340 cm/s) in the long-period (T > 3 s) band, which is potentially disastrous for high-rise buildings, large oil storage tanks, etc. to have longer resonant period. Such long-period motion was, for the most parts, developed by the static displacement of the fault movement rather than by the seismic waves radiating from the source fault. Thus, the extreme near-fault long-period motion was hazardous only close to the fault but it attenuated very rapidly away from the fault.

A comparative analysis of site-specific response spectral amplification models

In the framework of the Seismic Hazard Harmonization in Europe (SHARE) project, the Swiss Seismological Service (SED) has performed an evaluation of two procedures developed to produce soil amplification models for 5% damped pseudo-spectral acceleration response spectra, each using different parameters to describe the soil properties. The goal of the work presented here is to evaluate the statistical consistency of the methods, with particular regard to their applicability to engineering practice. Additionally, we compare the results with those from a methodology internally developed by the SED, which is based on spectral modeling of ground motion using the quarter-wavelength approximation to parameterize soil conditions. Soil amplification is computed with respect to reference rock condition as defined for the probabilistic seismic hazard assessment performed during the SHARE project.For the comparison, a residual analysis was performed between the computed soil-amplification functions from the three different methodologies, over a number of selected sites spanning different soil classes and ground motion levels. The analysis of the average residuals of these functions is useful to highlight the main differences between the proposed approaches, with special regard to the impact of soil resonances and anelastic attenuation within different frequency bands.The assessment was performed on a group of 88 selected stations of the Japanese KiKNet strong-motion network, for which complete logs of the shear-wave velocity profiles are available, in addition to a significant number of earthquake recordings. In a first step, average residuals were computed. Subsequently, amplification variability related to soil classes was investigated. The target of this second step was to perform the comparison by separately analyzing the impact of different soil and velocity classes, according to a soil-classification scheme proposed by Aristotle University of Thessaloniki (AUTH). In this paper the main results of these investigations are summarized and, when applicable, an interpretation of our findings is given.

Site amplification at the city scale in Basel (Switzerland) from geophysical site characterization and spectral modelling of recorded earthquakes

Hazard assessment at the city scale requires a detailed characterization of the effect of surface geology on ground motion (site effects). Though this analysis is commonly achieved using geophysical site characterization and site response modelling, we propose here a complementary analysis based on amplification functions retrieved from Empirical Spectral Modelling (ESM) of earthquake recordings. We applied this method to the city of Basel (Switzerland) that benefits from a detailed microzonation and a dense Strong Motion Network with 21 modern free-field stations. We first verified the accuracy of ESM amplification functions for this region and used them to determine the bedrock interface at a site with a detailed velocity profile. While the interface between Upper and Lower Tertiary was, until now, considered responsible for the fundamental frequency of resonance in the Rhine Graben, we found that the bedrock interface in fact lies at the Mesozoic limestone. We also investigated the second peak of the H/V ratios that is clustered in a particular area of the basin where amplification is found to be different. We successfully used the ESM amplification functions to verify the microzonation of 2006 and would strongly advise the installation of strong motion stations where such studies are performed in the future. Outside the Rhine Graben, where shallow sediments are found, we propose an amplification functional form based on ESM and the fundamental frequency of resonance. Finally, we combined all our findings and generated amplification maps of the response spectrum at any period of interest for earthquake engineering. This map is proposed for a high resolution real-time implementation in ShakeMap and will be used for seismic loss assessment.

BSHAP project strong ground motion database and selection of suitable ground motion models for the Western Balkan Region

The Harmonization of Seismic Hazard Maps in the Western Balkan Countries Project (BSHAP) was funded for 7 years by NATO Science for Peace and Security Program to support the preparation of new seismic hazard maps of the Western Balkan Region. In the framework of BSHAP, the regional free field strong motion network capacity was significantly increased by deployed recorders (Gulerce et al. in Final report of improvements in the Harmonized Seismic Hazard Maps for the Western Balkan Countries (BSHAP-2) Project, NATO SfP-984374. http://wbalkanseismicmaps.org/ , 2015) and the BSHAP strong motion database that includes both pre-BSHAP (mostly analogue) and post-BSHAP (all digital) recordings was compiled. The BSHAP strong motion database includes uniformly processed strong motions along with the related earthquake metadata and station information; therefore, it provides a solid base for the ground motion characterization studies in the region. The established database is used for selection of the ground motion prediction equations (GMPEs) to be employed in the probabilistic seismic hazard assessment by comparing the compiled strong ground motions with the predictions of candidate global and Euro-Mediterranean GMPEs in a systematic manner. Details of the selection strategy including the analysis of model predictions for ground motion scaling, data testing to evaluate the model performance, and ranking is provided here along with the GMPE logic tree used in the proposed seismic hazard maps by Kuka et al. (Bull Earthq Eng, under review).

Istanbul natural gas network rapid response and risk mitigation system

This paper describes a rapid response and risk mitigation system Istanbul Natural Gas Distribution Network Seismic Risk Reduction Project (IGRAS) for the Istanbul Natural Gas Network (IGDAŞ). Upon the trigger signal received from the earthquake early warning system in Istanbul, the real-time algorithm at IGRAS system district regulators checks the threshold levels of ground-motion parameters and interrupts the gas flow if any exceedance is detected. Then the system: (1) produces almost real-time earthquake hazard maps by using on-line strong-motion data from the strong-motion network in Istanbul: (2) estimates the distribution of damage to the natural gas network; and (3) transfers these damage distribution maps to stakeholders to enable dispatching rapid response teams to high damage areas.

Towards real-time earthquake impact alerting in Indonesia

Abstract The Government of Indonesia has committed to deploying a network of 500 strong-motion sensors throughout the nation. The data from these sensors have the potential to provide critical near-real-time information on the level of ground shaking and potential impact from Indonesian earthquakes near communities. We describe the implementation of real-time ‘ShakeMaps’ within Indonesia's Agency of Meteorology, Climatology and Geophysics (BMKG). These ShakeMaps are intended to underpin real-time earthquake situational awareness tools. The use of the new strong-motion network is demonstrated for two recent earthquakes in northern Sumatra: the 2 July 2013 M w 6.1 Bener Meriah, Sumatra and the 10 October 2013 M w 5.4 Aceh Besar earthquakes. The former earthquake resulted in 35 fatalities, with a further 2400 reported injuries. The recently integrated ShakeMap system automatically generated shaking estimates calibrated by BMKG's strong-motion network within 7 min of the Bener Meriah earthquake's origin, which assisted the emergency response efforts. Recorded ground motions are generally consistent with theoretical models. However, more analysis is required to fully characterize the attenuation of strong ground motion in Indonesia.

Assessing Components of Ground‐Motion Variability from Simulations for the Marmara Sea Region (Turkey)

Recent studies have shown that repeatable travel-path terms make a high contribution to the overall variability in earthquake ground motions. Having maps of such terms available for a given recording site would, theoretically, allow removal of this component from the aleatory variability of ground-motion models. The assessment of such travel path terms for a given site, however, relies on having recorded a rich set of earthquakes at that site. Given the relative youth of strong-motion networks the assessment of such terms from observations is currently difficult for most parts of the world. Ground-motion simulations, however, provide an alternative method to assess such terms. In this article many dozens of earthquakes, distributed in a grid, are simulated for the Marmara Sea region (Turkey), which borders the megacity of Istanbul and is an area of high seismic hazard. Ground motions are simulated within a detailed 3D velocity structure model using a finite-difference method at 70 recording sites in the area (200 x 120km). Horizontal peak ground velocities from these simulations are regressed to derive a ground-motion model. Next, residuals from these GMPEs are computed to assess repeatable source, site and path terms and various components of ground-motion variability. These components are similar to those derived from real strong-motion data, thereby lending support to those estimates as well as showing the worth of simulations for this type of exercise.

Strong-Motion Observations of the M 7.8 Gorkha, Nepal, Earthquake Sequence and Development of the N-SHAKE Strong-Motion Network

We present and describe strong-motion data observations from the 2015 M 7.8 Gorkha, Nepal, earthquake sequence collected using existing and new Quake-Catcher Network (QCN) and U.S. Geological Survey NetQuakes sensors located in the Kathmandu Valley. A comparison of QCN data with waveforms recorded by a conventional strong-motion (NetQuakes) instrument validates the QCN data. We present preliminary analysis of spectral accelerations, and peak ground acceleration and velocity for earthquakes up to M 7.3 from the QCN stations, as well as preliminary analysis of the mainshock recording from the NetQuakes station. We show that mainshock peak accelerations were lower than expected and conclude the Kathmandu Valley experienced a pervasively nonlinear response during the mainshock. Phase picks from the QCN and NetQuakes data are also used to improve aftershock locations. This study confirms the utility of QCN instruments to contribute to ground-motion investigations and aftershock response in regions where conventional instrumentation and open-access seismic data are limited. Initial pilot installations of QCN instruments in 2014 are now being expanded to create the Nepal–Shaking Hazard Assessment for Kathmandu and its Environment (N-SHAKE) network. Online Material: Figures of Pg arrivals, earthquake locations, epicenter change vectors, and travel-time misfit vector residuals, and tables of QCN and NetQuake stations and relocated hypocenter timing, location, and magnitude.

Characteristics of strong ground motions in the 2014 Ms 6.5 Ludian earthquake, Yunnan, China.

The 2014 M s 6.5 (M w6.1) Ludian earthquake occurred in the eastern Sichuan–Yunnan border region of western China. This earthquake caused much more severe engineering damage than the usual earthquakes with the same magnitude in China. The National Strong Motion Network obtained large set of ground motion recordings during the earthquake. To investigate the engineering interested characteristics of ground motion from Ludian earthquake and compare it with the M w 7.9 Wenchuan and the M w 6.6 Lushan earthquakes in western China, studies on the ground motion field, attenuation relationship, distance dependence of significant duration, and site amplification were carried out. Some conclusion is drawn. Specifically, the ground motion field reveals a directional feature, and the distribution characteristics of the two horizontal components are similar. The attenuation relationship for Ludian earthquake is basically consistent with the ground motion prediction equation (GMPE) for western China, except the slight smaller than the GMPE predicted at short periods. The distance dependences of ground motion duration are different in Sichuan and Yunnan regions due to the local physical dispersion and Q value. The site amplification factors are dominated by linear site response for lower reference ground motion, but the nonlinearity becomes notable for higher reference ground motion. This feature is basically consistent with the empirical model for western China. All the results indicate that the spatial distribution of ground motion, the attenuation characteristics, and the site amplification effect should be considered in characterization of near-field ground motion.

Limits on the potential accuracy of earthquake risk evaluations using the L’Aquila (Italy) earthquake as an example

<p>This article is concerned with attempting to ‘predict’ (hindcast) the damage caused by the L’Aquila 2009 earthquake (M<sub>w</sub> 6.3) and, more generally, with the question of how close predicted damage can ever be to observations. Damage is hindcast using a well-established empirical-based approach based on vulnerability indices and macroseismic intensities, adjusted for local site effects. Using information that was available before the earthquake and assuming the same event characteristics as the L’Aquila mainshock, the overall damage is reasonably well predicted but there are considerable differences in the damage pattern. To understand the reasons for these differences, information that was only available after the event were include within the calculation. Despite some improvement in the predicted damage, in particularly by the modification of the vulnerability indices and the parameter influencing the width of the damage distribution, these hindcasts do not match all the details of the observations. This is because of local effects: both in terms of the ground shaking, which is only detectable by the installation of a much denser strong-motion network and a detailed microzonation, and in terms of the building vulnerability, which cannot be modeled using a statistical approach but would require detailed analytical modeling for which calibration data are likely to be lacking. Future studies should concentrate on adjusting the generic components of the approach to make them more applicable to their location of interest. To increase the number of observations available to make these adjustments, we encourage the collection of damage states (and not just habitability classes) following earthquakes and also the installation of dense strong-motion networks in built-up areas.</p>

Correlations between structural damage and ground motion parameters during the Ms8.0 Wenchuan Earthquake

The Wenchuan Earthquake with a magnitude of Ms 8.0 struck the Sichuan province of China on May 12, 2008, where it mainly affected the area along the Longmenshan fault. In total, 420 three-component acceleration records were obtained by the China Strong Motion Networks Centre during this seismic event, among which over 50 records exceeded 100gal. In the present study, we collected 48 near-fault acceleration records to derive strong ground motion parameters in terms of the peak ground acceleration, peak ground velocity, peak spectrum acceleration (5% of the damping ratio) and spectrum intensity (5% of damping ratio). We determined the building collapse ratios (CRs) for 20 targeted districts based on data acquired from both the China Earthquake Administration and the Chinese Academy of Sciences, where the CRs combined the data for all building types. Fragility curves were established between the CRs and the corresponding ground motion parameters, based on which the damage criteria were proposed. In particular, we derived the fragility curves for brick-concrete structures and frame-structures. These curves indicate how different structural types can determine the damage sustained. In addition, we developed a method for estimating building damage classifications. If we assume that buildings are built according to the improved Seismic Fortification Criterion in the revised “Code for Seismic Design of Buildings”, the predicted CRs for the 20 targeted districts would be significantly lower compared with the actual damage they sustained, which illustrates the validity of both the method and the revised code.

British Columbia Smart Infrastructure Monitoring System

This paper describes the architecture of a comprehensive seismic monitoring system developed in 2009 by the British Columbia Ministry of Transportation and Infrastructure (MoT) and the University of British Columbia, Canada. The main purpose of the British Columbia Smart Infrastructure Monitoring System project is to instrument and monitor key structures to provide confirmation of their seismic capacity, assist in focusing retrofit efforts, detect structural damage, and provide rapid damage assessment of those structures, following a seismic event. The automatic creation of shakemaps following an earthquake provides information for the MoT’s non-instrumented bridges. The public notification systems and web pages have been developed to display real-time seismic data both from the strong motion network and seismic structural health monitoring network. Tools and methods have been developed to help transform the current practice of inspecting and evaluating structures to a more rational and effective one that uses the up-to-date sensing technology with fast and efficient techniques.

Strong Motion Observation from Recent Destructive Earthquakes in China Mainland

Strong earthquake motion observations have gathered much useful data for the seismic-resistant design of civil engineering structures, and for developing earthquake prevention technology. The performance of Chinese strong motion network has been evaluated from recent earthquakes in Chinese Mainland. To follow the new requirement of the earthquake mitigation plan, some new practice of strong motion observations are described, including rapid urban ShakeMap, earthquake early warning system.

Seismic response of an 8-story RC-building from ambient vibration analysis

In this study, we assess the dynamic characteristics of an 8-story RC-building composed by two units connected through a structural joint. This building, belonging to one of the largest hospitals in northern Greece, has been selected in the framework of an European funded project as test site for developing a structural health monitoring system and it is instrumented with a permanent strong motion network. The assessment of the dynamic characteristics is performed using ambient vibration recorded by a temporary seismic network installed inside the structure. Non-parametric identification methods, namely the peak picking and frequency domain decomposition, are applied to perform operational modal analysis and extract the natural frequencies and mode shapes of the structural system. Since the detection of changes in the shear wave velocity inside the building is relevant for health monitoring analysis, we use the ambient vibration recordings to perform a deconvolution interferometry. Moreover, a shear-beam model is considered to estimate the velocity in the first three floors, where the distribution of internal sources introduces complex patterns in the impulse response functions. The velocity for lowest part of the building is estimated by optimizing the match between the arrival times of the empirical and theoretical pulses. Finally, the velocities and quality factors estimated from ambient vibration analysis are consistent with preliminary results obtained analyzing earthquake data recorded in the same building.

Assessment of Site Effects in Alpine Regions through Systematic Site Characterization of Seismic Stations

Abstract In the framework of the renewal project of the Swiss Strong Motion Network (SSMNet), a procedure for site characterization has been established. The aim of the procedure was to systematically derive realistic 1D velocity profiles at each station. It is mainly based on the analysis of surface waves, particularly from passive experiments, and includes cross checks of the derived amplification functions with those obtained through spectral modeling of recorded earthquakes. The systematic use of three component surface‐wave analysis, allowing the derivation of both Rayleigh and Love dispersion curves, also contributes to the improvement of the quality of the retrieved profiles. The procedure is applied to the 30 SSMNet stations installed on various site types within the project, covering different aspects of seismic risk. The characterization of these 30 sites gives an overview of the variety of possible effects of surface geology on ground motion in the Alpine area. Such effects ranged from deamplification at hard‐rock sites to amplification up to a factor of 15 in lacustrine sediments with respect to the Swiss reference rock velocity model. The derived velocity profiles are shown to reproduce observed amplification functions from empirical spectral modeling. Although many sites are found to exhibit 1D behavior, the procedure allows the detection and qualification of 2D and 3D effects. The sites are therefore classified with respect to the occurrence of 2D/3D resonance and edge‐generated surface waves. In addition to the large and deeply incised alpine valleys of the Rhone, the Rhine, and the Aar, smaller structures such as local alpine valleys and alluvial fans are shown to exhibit 2D/3D behavior.

An empirical equation of effective shaking duration for moderate to large earthquakes

The duration of strong shaking is particularly important for assessing building performance, potential landslides and liquefaction hazards. The results of this investigation can potentially help reduce related fatalities and economic losses. In this study, we ana- lyzed the acceleration seismograms of the Taiwan strong motion network to characterize the strong shaking duration associated with earthquake sources, propagation paths and site effects. This study proposes a new definition for the strong shaking duration called ''effective shaking duration'' (ESD), which considers the amplitude and radiation energy decays. We first consider the window of a time series during which the amplitude is C0.01 g, and we then defined the ESD as the length of the interval of the dissipated energy within 5-95 % of the total energy during this time frame. We calculated the strong shaking duration for 495 inter-plate events with magnitudes of ML ( 5.0 and focal depths\50 km in the Taiwan region from 1994 to 2012. Using a nonlinear regression procedure, we thus obtained an empirical equation for strong shaking durations. The equation is a function of earthquake magnitude, distance and site conditions, which are defined by the Vs30 value (the S-wave velocity structure of the top 30 m of the site). The results indicate that the shaking durations significantly increase with magnitude and also decrease with distance and Vs30. Compared with empirical equations from global datasets, our empirical equation is applicable to earthquakes in other regions and will produce smaller but more applicable duration values for smaller earthquakes. However, for larger events, our ESD values are comparable with those derived from other definitions (e.g., significant duration). Although the empirical relationship is mainly based on Taiwanese events, in view of the massive dataset, this empirical equation could provide important information to the global com- munity regarding the ground shaking duration estimation in the ground motion prediction of future earthquakes.

Coda wave attenuation characteristics for Kumaon and Garhwal Himalaya, India

Uttarakhand Himalayas are among one of the most seismically active continental regions of the world. The Himalayan belt in this region is divided into Kumaon and Garhwal Himalaya. The Kumaon Himalayas has not experienced any large earthquake in the recent past; however, this region is frequently visited by small-magnitude earthquakes. The objective of this paper was to determine regional attenuation characteristics from data recorded by local strong motion networks operating in these two regions, using coda waves. Coda wave quality factor estimates for the Kumaon and the Garhwal Himalaya region have been made in high-frequency range using single backscattering model given by Aki and Chouet (J Geophys Res 80:3322–3342, 1975). Coda waves of 30-s window length, filtered at six different frequency bands, centered at 1.5, 3.0, 6.0, 12.0, 20.0 and 28.0 Hz, have been analyzed using the single backscattering method. The frequency-dependent Q c(f) relationship for the Kumaon and Garhwal Himalaya was obtained as Q c = (65 ± 2.4)f (1.07±.04) and Q c = (96 ± 6.9)f (1.06±.04), respectively, which indicate a higher attenuating medium in the Kumaon Himalaya as compared to Garhwal Himalaya. The obtained difference of attenuation characteristics in this region is further compared with the rate of decay of peak ground acceleration with respect to magnitude and distance parameters by using regression model of peak ground acceleration obtained from available strong motion data in this region. Present studies clearly indicate that there is good evidence for high rate of attenuation in the Kumaon Himalaya as compared to the Garhwal Himalaya.

Strong-Motion Observations of the Lushan Earthquake on 20 April 2013

Online Material: Additional figures of acceleration time series; table of station parameters, associated ground motion intensities. On 20 April 2013, at 08:02 a.m. Beijing time, a strong earthquake hit Lushan, a county in the southwest of Sichuan Province in China. During this earthquake, a total of 114 strong‐motion stations from the new generation of the National Strong‐Motion Observation Network System (NSMONS) of China were triggered. The NSMONS consists of 1154 permanent free‐field stations and began to operate in March 2008. The 2008 Wenchuan destructive earthquake triggered a large number of strong‐motion recordings that contribute significantly to the world strong‐motion database (Li, Zhou, Huang, et al. , 2008). The 2013 Lushan earthquake also provided a large number of near‐source recordings in China (Xie et al. , 2014). NSMONS aims to enhance the ability of earthquake monitoring and the collection of strong‐motion recordings in the most seismically active regions and some major cities in the Chinese mainland. As a result, its free‐field stations are irregularly distributed with an average spacing of 50 km to hundreds of kilometers (Li, Zhou, Yu, et al. , 2008). Thus, it definitely cannot monitor all of the seismic areas in China. For example, on 14 April 2010, the Yushu earthquake, which exhibited a magnitude of M s 7.1, occurred in the northeast part of the Tibetan plateau at Yushu, Qinghai Province. Only five strong‐motion stations of NSMONS were triggered, the nearest of which was approximately 350 km from the epicenter, and the maximum peak ground acceleration (PGA) was only approximately 2 cm/s2. Taking into account the randomness of the spatial distribution of earthquakes, most strong‐motion recordings obtained in recent years have small amplitudes and are thus not of interest to engineers (China Strong Motion Networks Center, 2012). As a result, these recordings only contribute to the steady growth of the strong‐motion …

Data Processing and Preliminary Analysis of Strong Motion Records from the Ms7.0 Lushan, China Earthquake

At 8:02 a.m. Beijing time on April 20, 2013, an Ms 7.0 earthquake shook the city of Ya’an, China. Until 24:00:00 on 20 July 2013, a total of 339 strong-motion records from 113 free-field stations, 21 records from 1 strong-motion structure array and 1123 groups of aftershock records have been collected, processed and analyzed preliminarily by the China Strong Motion Network Center (CSMNC) in this paper. There are more than 26 stations located within Longmenshan fault zone and all peak ground acceleration (PGA) of records is larger than 50gal. The PGA of Baoxingdiban station reaches 1005.4 gal after zero-line initialization, which firstly breaks through 1g in the mainland of China. Based on the mainshock records, shakemaps of those PGAs are plotted and attenuation relationships of PGAs are presented in this article.