Kinematic deformation and intensity assessment of the 2021 Maduo M_(S)7.4 earthquake in Qinghai revealed by high-frequency GNSS

Rapid acquisition of the kinematic deformation field and seismic intensity distribution of large earthquakes is crucial for postseismic emergency rescue,disaster assessment,and future seismic risk research.The advancement of GNSS observation and data processing makes it play an important role in this field,especially the high-frequency GNSS.We used the differential positioning method to calculate the 1 HZ GNSS data from 98 sites within 1000 km of the M_(S)7.4 Maduo earthquake epicenter.The kinematic deformation field and the distribution of the seismic intensity by using the peak ground velocity derived from displacement waveforms were obtained.The results show that:1)Horizontal coseismic response deformation levels ranging from 25 mm to 301 mm can be observed within a 1000 km radius from the epicenter.Coseismic response deformation on the east and west sides shows bilateral asymmetry,which markedly differs from the symmetry presented by surface rupture.2)The seismic intensity obtained through high-frequency GNSS and field investigations exhibits good consistency of the scope and orientation in the high seismic intensity area,although the former is generally slightly smaller than the latter.3)There may exist obstacles on the eastern side of the seismogenic fault.The Maduo earthquake induced a certain tectonic stress loading effect on the western Kunlun Pass-Jiangcuo fault(KPJF)and Maqin-Maqu segment,resulting in higher seismic risk in the future.

Seismic fragility analysis of clay-pile-pier systems considering the optimization of ground motion intensity measures

The performance of clay-pile-pier system under earthquake shaking was comprehensively examined via three-dimensional finite element analyses,in which the complex stress-strain relationships of a clay and piled pier system were depicted by a hyperbolic-hysteretic and an equivalent elastoplastic model,respectively.One hundred twenty ground motions with varying peak accelerations were considered,along with the variations in bridge superstructure mass and pile flexural rigidity.Comprehensive comparison studies suggested that peak pile-cap acceleration and peak pile-cap velocity are the optimal ground motion intensity measures for seismic responses of the pier and the pile,respectively.Furthermore,based on two optimal ground motion intensity measures and using curvature ductility to quantify different damage states,seismic fragility analyses were performed.The pier generally had no evident damage except when the bridge girder mass was equal to 960 t,which seemed to be comparatively insensitive to the varying pile flexural rigidity.In comparison,the pile was found to be more vulnerable to seismic damage and its failure probabilities tended to clearly reduce with the increment of pile flexural rigidity,while the influence of the bridge girder mass was relatively minor.

Vector-intensity measure based seismic vulnerability analysis of bridge structures

This paper presents a method for seismic vulnerability analysis of bridge structures based on vector-valued intensity measure （viM）, which predicts the limit-state capacities efficiently with multi-intensity measures of seismic event. Accounting for the uncertainties of the bridge model, ten single-bent overpass bridge structures are taken as samples statistically using Latin hypercube sampling approach. 200 earthquake records are chosen randomly for the uncertainties of ground motions according to the site condition of the bridges. The uncertainties of structural capacity and seismic demand are evaluated with the ratios of demand to capacity in different damage state. By comparing the relative importance of different intensity measures, Sa（T1） and Sa（T2） are chosen as viM. Then, the vector-valued fragility functions of different bridge components are developed. Finally, the system-level vulnerability of the bridge based on viM is studied with Duunett- Sobel class correlation matrix which can consider the correlation effects of different bridge components. The study indicates that an increment IMs from a scalar IM to viM results in a significant reduction in the dispersion of fragility functions and in the uncertainties in evaluating earthquake risk. The feasibility and validity of the proposed vulnerability analysis method is validated and the bridge is more vulnerable than any components.

The 2018 M_S 5.9 Mojiang Earthquake:Source model and intensity based on near-field seismic recordings

On September 8, 2018, an M_S 5.9 earthquake struck Mojiang, a county in Yunnan Province, China. We collect near-field seismic recordings(epicentral distances less than 200 km) to relocate the mainshock and the aftershocks within the first 60 hours to determine the focal mechanism solutions of the mainshock and some of the aftershocks and to invert for the finite-fault model of the mainshock.The focal mechanism solution of the mainshock and the relocation results of the aftershocks constrain the mainshock on a nearly vertical fault plane striking northeast and dipping to the southeast. The inversion of the finite-fault model reveals only a single slip asperity on the fault plane. The major slip is distributed above the initiation point, ～14 km wide along the down-dip direction and ～14 km long along the strike direction, with a maximal slip of ～22 cm at a depth of ～6 km. The focal mechanism solutions of the aftershocks show that most of the aftershocks are of the strike-slip type, a number of them are of the normal-slip type, and only a few of them are of the thrust-slip type.On average, strike-slip is dominant on the fault plane of the mainshock, as the focal mechanism solution of the mainshock suggests, but when examined in detail, slight thrust-slip appears on the southwest of the fault plane while an obvious part of normal-slip appears on the northeast, which is consistent with what the focal mechanism solutions of the aftershocks display. The multiple types of aftershock focal mechanism solutions and the slip details of the mainshock both suggest a complex tectonic setting, stress setting, or both. The intensity contours predicted exhibit a longer axis trending from northeast to southwest and a maximal intensity of Ⅷ around the epicenter and in the northwest.

Some considerations on the physical mea-sure of seismic intensity

The study on seismic intensity can be traced prior to the time that modern seismology was established. In its early stage the seismic intensity was designed to serve as a measure in scaling the severity of earthquake damage to civil engineering and environmental structures. Also the seismic intensity is usually assigned by engineers and seismologists with one or two characteristic parameters of earthquake ground motions to reflect earthquake damage potential so as to be able to serve as an input earthquake load for seismic design of structures. So choosing a proper parameter to reflect the action of seismic intensity is the main objective of the research on physical measure of seismic intensity. However, since various kinds of structures have quite different damage mechanisms, there will exist great differences in damages to different structures located at the same area during the same earthquake. Particularly, in some cases, quite different damages have happened even to the structures of same kind due to many other factors such as different construction materials, different configurations or on the different types of sites where structures located. In addition, the ground motion parameters, which result in damage to structures, are not the single peak value of ground motion. Hence, this paper emphasizes that the research on new physical measure of seismic intensity should not only consider the structural characteristics but also take into account other parameters such as duration, energy of ground motion and so on. In particular, as the physical measures of intensity, different ground motion parameter should be adopted for different structures.

Detailed seismic zoning of the East Kazakhstan region in the Republic of Kazakhstan

Kazakhstan is currently drafting new construction regulations that comply with the major provisions of the Eurocodes.Such regulations are created on the basis of seismic zoning maps of various degrees of detail,developed by our Institute of Seismology using a new methodological approach for Kazakhstan.The article is about creating the first normative map of the Detailed Seismic Zoning on a probabilistic foundation for the Republic of Kazakhstan’s East Kazakhstan region.We carried out the probabilistic assessment of seismic hazard using a methodology consistent with the main provisions of Eurocode 8and updated compared with that used in developing maps of Kazakhstan’s General Seismic Zoning and seismic microzoning of Almaty.The most thorough and current data accessible for the area under consideration were combined with contemporary analytical techniques.Updates have been done to not only the databases being used but also the way seismic sources were shown,including active faults now.On a scale of 1:1000000,precise seismic zoning maps of the East Kazakhstan region were created for two probabilities of exceedance:10%and 2%in 50 years in terms of peak ground accelerations and macroseismic intensities.The obtained seismic hazard distribution is generally consistent with the General Seismic Zoning of Kazakhstan’s previous findings.However,because active faults were included and a thoroughly revised catalog was used,there are more pronounced zones of increased danger along the fault in the western part of the region.In the west of the territory,acceleration values also increased due to a more accurate consideration of seismotectonic conditions.Zoning maps are the basis for developing new state building regulations of the Republic of Kazakhstan.

Seismic intensity investigation of the 2001 M=6.0 Yajiang-Kangding earthquake and discussion on its background of seismogenic structures

An M=6.0 earthquake occurred on February 23, 2001 in the western Sichuan Province, China. The macro seismic epicenter situated in the high mountain-narrow valley region between Yajiang and Kangding counties. According to field investigation in the region, the intensity of epicentral area reached VIII and the areas with intensity VIII, VII and VI are 180 km2, 1 472 km2 and 3 998 km2, respectively. The isoseismals are generally in elliptic shape with major axis trending near N-S direction. The earthquake destroyed many buildings and produced some phenomena of ground failure and mountainous disasters in the area with intensity VIII. This event may be resulted from long-term activities of the Litang fault and Yunongxi fault, two main faults in the western Sichuan. The movements between the main faults made the crust stress adjusted and concentrated, and finally the earthquake on a secondary fault in the block released a quite large energy.

Research on seismic intensity zonation by use of the response intensity of historical earth－quakes───with the central part of Shanxi Province as an example

With the central part of Shanxi Province as an example, this paper studied seismic intensity zonation directly by use of the response intensity of historical earthquakes. From the result, some conclusions can be drawn as follows: ① For areas rich in data of historical earthquakes, the seismic intensity zonation map with probabilistic meanings can be compiled by use of the statistical features of the response intensity of sites; ② When determining the length of time for statistics, the completeness of response intensity data and the inhomogeneity of regional seismic activities should be fully considered; ③ By comparing the seismic intensity zonation result for recurrence interval of 500 years with the new Seismic Intensity Zonation Map of China (1990), it has been found that the two are roughly similar; though they are somewhat different for some localities, each has its own reasonableness.

Method of expected earthquake losses estimation based on the frequency of seismic site intensity

During a given period,a site will suffer the attack from earthquake several times.But this effect is neglected in the currently used model of loss estimation from earthquake When calculating the occurrence rate of the affected intensity,the difference of the exceeding probability is used.Such treatment will underestimate the earthquake loss,especially when the exposure period is long.To overcome the shortcomings of the model currently used,a new frame of earthquake loss estimation is provided from the logic sense:during the given period,the expected earthquake loss responding to the specific affected intensity is equal to the expected number of the intensity multiplying the expected loss under the condition of such an affected intensity,and the total expected loss is equal to the effects of all the possible intensities.On the basis of the seismicity model used in compiling the 'Chinese Seismic Intensity Zoning Map(1990) ',a new formula of expected loss evaluation and the variance of the evaluation are provided.It is inferred from the example and the comparison with the currently used method that the new method is applicable and necessary.These results will lay a scientific foundation for the estimation of earthquake loss,insurance and disaster prevention.

A new type seismic intensity meter

A new type of seismic intensity meter based on MEMS accelerometer is introduced. It employs STM32FI07 as the data processing core and detects the changes of acceleration with triaxial MEMS LIS344ALH and uses ADS1248 for 24 bit data sampling. The test on vibration table shows that the linearity of the meter is δL = ± 1.4% , and the sensitivity is Kc = 0.9671V/g with zero deviation of 0.0043 g. The seismic intensity meter has the advantages of simple structure and stable performance and it is appropriate for intensive layout on a large scale.

Intensity-frequency Estimation Based on Historical Seismic Intensity in the Yunnan Area

For earthquake disaster mitigation,we use historical records and more complete intensity investigation data from 1500 to 2015 to analyze and estimate the seismic intensity and frequency of the earthquake-prone areas in Yunnan. We digitized intensity observations and divided the Yunnan region into cell size of 0. 2°× 0. 2° to calculate the seismic intensity-frequency relationship for each cell. Combined with a repeated cycle of intensity of one hundred years and population economics data in Yunnan,we analyze future areas of concern. The results can provide a reference for earthquake hazardous area zoning.This method is based on historical earthquake data,reducing as much as possible the various hypotheses for the assessment,and thus can concisely reflect the different intensityfrequency distributions of the region.

Parameter Fitting of Seismic Intensity Attenuation Model in Xinjiang

By using the existing historical earthquake investigation data in Xinjiang,this paper obtained the envelope curves of isoseismal maps of 103 destructive earthquakes occurring from 1716 to 2010 after digitization of the data. The author summarized the seismic intensity attenuation laws in the Xinjiang region with the multiple regression fitting method. The intensity attenuation function of the elliptical model was provided and the fitting results in different periods and areas were compared. Finally, the intensity attenuation relationship in the Xinjiang region was obtained by the method of constraining the start and end of the attenuation curves.

Damage and Seismic Intensity in the Meizoseismal Region of the M_S8.0 Wenchuan Earthquake,Sichuan,China

This paper presents the damage in the meizoseismal region of the M_S8.0 Wenchuan earthquake,Sichuan,China,and the seismic intensities determined according to "the Chinese Seismic Intensity Scale",and discusses briefly the types of earthquake-generating faults and some features of seismic damage.

Discussion on the Seismic Intensity of the Hutubi Ms6.2 Earthquake on December 8,2016

Based on the field investigation of 182 seismic hazard survey sites,combined with analysis of the aftershock sequence, focal mechanism, and seismo-tectonic background, we produced the seismic intensity map of the Hutubi M_S6.2 earthquake. The seismic intensity of the magistoseismic area is degree Ⅷ,with the orientation of long axis of isoseismic contour lines east-west. The Qingshuihezi fault is considered as the seismogenic fault of Hutubi M_S6.2

Analysis of Seismic Risk at an Engineering Site from Site Effect Seismic Intensity Data Using the Seismotectonic Method——Taking Six Reservoir Dam Sites in Western Anhui as an Example

The seismotectonic method is used to study the seismogenic structures and the maximum potential earthquake around an engineering site in order to determine the seismic risk at the site. Analysis of seismic risk from site effect seismic intensity data, in combination with regional seismo_geological data, using the seismotectonic method can provide a more reliable result. In this paper, taking the area of six reservoir dam sites in western Anhui as an example, we analyze the seismic risk from site effect seismic intensity data in combination with the seismotectonic conditions and find that P (I≥i)=10% over 50 years. The result shows that the seismogenic structure and the maximum potential earthquake have a controlling effect on seismic risk from future earthquakes in the area around the site.

Seismic Intensity Zoning Map of China (1990) and Its Explanation

The Seismic Intensity Zoning Map of China(1990)was based on the probabilistic method of seismic hazard analysis.In compiling the map,the characteristics of inhomogeneity of earthquake distribution both in space and time in China are considered sufficiently,and some necessary modifications in the model of seismic hazard analysis are carried out.Based on the analysis of the seismic activity and seismotectonic environment,26 seismic provinces are divided first as the statistical elements of the seismicity analysis; the seismic potential source areas are then divided in the seismic provinces.The 733 potential source areas with various upper limit magnitudes have been divided in the country.According to the reliable time domain of earthquake data with various magnitude intervals,the b values in magnitude-frequency relationship are calculated in the seismic provinces.According to the analysis of the inhomogeneity of seismicity distribution both in space and time,the annual average occurrence rates of the

New Physical Measures of Seismic Intensity

The physical measures of macroscopic seismic intensity have been extensively studied based on the new understanding of seismic intensity and the new analytical method and new database of strong ground motion.New physical measures of seismic intensity have been proposed.

Analysis of Seismic Risk by Using Site Earthquake Response Intensity

Based on the site historical earthquake data,a method of seismic risk analysis is presented.Once the frequency of earthquake response intensity and the relative value showed a logarithmic linear,the maximum similarity method would be used to obtain β,λ,and Imax,and also achieve the results of risk analysis on each site.At the same time,the "logic tree" method can be used to calibrate the uncertainty of the risk on each site.Then the final results of risk analysis indicate that this method is feasible,particularly for the sites showing intensity anomaly.

Preface to the special issue on Earthquake early warning system and rapid seismic instrumental intensity report

In the past several years, from May 12, 2008 Wenchuan Mw8.0 earthquake in China to March 11, 2011 off the Pacific coast of Northeastern Mw9.0 earthquake in Japan, the world witnessed catastrophic disasters caused by destructive earthquakes. The earthquake posed a great threat to the development of society and economy, especially in the developing countries such as China. In order to reduce the losses in peoples life and properties in maximum possibilities, there were a lots of technologies had been researched and developed, among them the earthquake early warning system （EEWS） and rapid seismic instrumental intensity report （RSIIP） are the two of the state-of-the-art technologies for the purpose. They may be used to minimize property damage and loss of life and to aid emergency response after a destructive earthquake.