Seismic Reduction and Isolation Design Strategies for Bridges in High-Intensity Earthquake Areas

High-intensity earthquakes can cause severe damage to bridges,buildings,and ground surfaces,as well as disrupt human activities.Such earthquakes can create long-distance,high-intensity surface movements that negatively impact bridge structures.This article delves into the seismic reduction and isolation design strategies for bridges in high-intensity earthquake areas.It analyzes various seismic reduction and isolation technologies and provides case studies to help relevant units understand the design strategies of these technologies.The results of this article can be used as a guideline to effectively enhance the seismic performance of bridges in high-intensity earthquake areas.

Seismic response of a mid-story isolated structure considering SSI in mountainous areas under long-period earthquakes

At present,there is not much research on mid-story isolated structures in mountainous areas.In this study,a model of a mid-story isolated structure considering soil-structure interaction(SSI)in mountainous areas is established along with a model that does not consider SSI.Eight long-period earthquake waves and two ordinary earthquake waves are selected as inputs for the dynamic time history analysis of the structure.The results show that the seismic response of a mid-story isolated structure considering SSI in mountainous areas can be amplified when compared with a structure that does not consider SSI.The structure response under long-period earthquakes is larger than that of ordinary earthquakes.The structure response under far-field harmonic-like earthquakes is larger than that of near-fault pulse-type earthquakes.The structure response under near-fault pulse-type earthquakes is larger than that of far-field non-harmonic earthquakes.When subjected to long-period earthquakes,the displacement of the isolated bearings exceeded the limit value,which led to instability and overturning of the structure.The structure with dampers in the isolated story could adequately control the nonlinear response of the structure,effectively reduce the displacement of the isolated bearings,and provide a convenient,efficient and economic method not only for new construction but also to retrofit existing structures.

Reactive Transport Process of Earthquake-induced Hydrochemical Changes in Guanding Thermal Spring,Western Sichuan,China

Earthquake-related hydrochemical changes in thermal springs have been widely observed;however,quantitative modeling of the reactive transport process is absent.In the present study,we apply reactive transport simulation to capture the hydrochemical responses in a thermal spring following the Wenchuan Ms 8.0 and Lushan Ms 7.0 earthquakes.We first constrain deep reservoir geothermal fluid compositions and temperature by multicomponent geothermometry,and then a reactive geochemical transport model is constructed to reproduce the hydrochemical evolution process.The results show that the recharge from the shallow aquifer increases gradually until it reaches a peak because of the permeability enhancement caused by the Lushan earthquake,which may be the mechanism to explain the earthquake-related hydrochemical responses.In contrast to the postseismic effect of the Wenchuan earthquake,the chemical evolution can be considered as hydrochemical anomalies related to the Lushan earthquake.This study proves that the efficient simulation of reactive transport processes is useful for investigating earthquake-related signals in hydrochemical time series.

Intermediate to Long-term Estimation of Strong Earthquake Risk Areas in the Chinese Mainland Based on Geodesic Measurements

Based on previous research results,present-day crustal deformation and gravity fields in the Chinese mainland are analyzed using the GPS data,leveling,gravity and cross-fault deformations. We analyzed strain accumulation of the major faults,and identified locked or high strain accumulation segments. Combining the effects of large earthquakes in the study area,the long-term (decade) probability of large earthquakes in the Chinese mainland is estimated.

Discussion on Principles and Methods in Estimating the Maximum Potential Earthquakes in Low Seismicity Areas

Five principles and methods are proposed for estimating the maximum potential earthquakesin low seismicity areas,and their applicabilities are discussed,taking Sichuan basin as asample area.The proposed principles and methods are not only on the grounds of thegeological tectonics but also considered fully the mutual complementation between geologicaland seismological methods.They will be helpful to the study of engineering seismology andthe assessment of designing ground motion parameters in low seismicity areas.

Discussion on Deep Tectonic Background of Moderately Strong Earthquake in Anhui Province and Its Neighboring Areas Using Results of Seismic Tomography

Using the latest results of seismic tomography, we studied the deep tectonic settings of the moderate and strong earthquakes in Anhul Province and its neighboring areas （28° - 39°N, 112°- 124°E）. The results are as follows： （1） There exists a certain correlation between the location of moderate-strong earthquake, the geologic structure of the surface and the partitioning of active tectonic elements with the upper-crust velocity structure. Most earthquakes recording M ≥ 6.0 occur in high-velocity zones or in the transitional areas between high-velocity and low-velocity zones in the upper crust. Seismicity in the low-velocity zone has a lesser impact. Earthquakes occuring in the high-velocity zone are distributed mainly in the velocity variation area. The boundary belts and the interior of the North China plain fault block are the main active sites of moderate-strong earthquakes. Beneath the fault basins in the western and northern sides of the block, the upper crust is characterized by a wide discontinuous distribution in the low-velocity zone, and in the transition zone from the low- to high velocities, the moderate strong seismicity shows a zonal distribution where active faults are developed. The NW-extension Zhoukou-Hefei-Xuancheng low-velocity zone separates the highvelocity zones of Dabieshan Mountains and west Shandong-Anhul, and moderate-strong earthquakes on its northern side bordering the high-velocity zones are relatively frequent. This low-velocity zone is probably an important and deeply structured boundary between the North China and the South China tectonic provinces. （2） The frequent moderate-strong earthquake recorded in the past and the recent small earthquake activities in the Huoshan-Lu＇ an area are the result of a low-velocity zone in the middle crust beneath the central part of Dabieshan and the two sets of deep faults that cut through the crust. （3） In terms of deep structures, the distribution of moderate-strong earthquake in Anhui Province has an obvious regional feature. Based on historical earthquake recurrence intervals and analogue principles of deep seismogenic tectonics, the potential earthquake risk zones recording Ms5.0 in Anhui Province are determined.

E-commerce Development Strategies of Agriculture-related Enterprises in Earthquake Area

The problems existing in the development of agriculture-related enterprises in earthquake area are evaluated,as well as the prominent issues existing in the process of developing E-commerce,consequently,the corresponding strategies for developing E-commerce in agriculture-related enterprises are proposed.

Emergency assessment of seismic landslide susceptibility: a case study of the 2008 Wenchuan earthquake affected area

The 8.0 Mw Wenchuan earthquake triggered widespread and large scale landslides in mountainous regions. An approach was used to map and assess landslide susceptibility in a given area. A numerical rating system was applied to five factors that contribute to slope instability. Factors such as lithology, topography, streams and faults have an important influence as event-controlling factors for landslide susceptibility assessment. A final map is provided to show areas of low, medium, and high landslide susceptibility. Areas identified as having high landslide susceptibility were located in the central, northeastern, and far south regions of the study area. The assessment results will help decision makers to select safe sites for emergency placement of refuges and plan for future reconstruction. The maps may also be used as a basis for landslide risk management in the study area.

Earthquake risk assessment for Istanbul metropolitan area

The impact of earthquakes in urban centers prone to disastrous earthquakes necessitates the analysis of associ- ated risk for rational formulation of contingency plans and mitigation strategies.In urban centers,the seismic risk is best quantified and portrayed through the preparation of'Earthquake Damage and Loss Scenarios.'The components of such scenarios are the assessment of the hazard,inventories and the vulnerabilities of elements at risk.For the development of the earthquake risk scenario in Istanbul,two independent approaches,one based on intensities and the second on spectral displacements,are utilized.This paper will present the important features of a comprehensive study,highlight the method- ology,discuss the results and provide insights to future developments.

Evaluation of a traditional method for peak flow discharge estimation for floods in the Wenchuan Earthquake area,Sichuan Province,China

Peak discharge of flood in small mountainous watershed is usually calculated using the "Rainstorm–runoff calculation method in small watersheds in Sichuan Province"(RRM). This study evaluated the RRM calculation using real-time monitored rainfall and hydrologic data from a small watershed in the Wenchuan Earthquake area of Sichuan Province, China. The results indicated that the discharge values given by the RRM are commonly overestimating the measured discharge. The overestimation rate was discussed and empirical equations were proposed for improving RRM estimations, based on the relationship between calculated and measured discharge values at different watershed scales(2, 30, and 40 km2), under different rainfall probabilities(0.97–0.5, 0.5–0.2, and 0.2–0.002), and for different rainfall durations(0–6, 6–24, and >24 h). The results of this study help contribute to the understanding of water floods formation and help provide more accurate estimations of peak flow discharge in small watersheds in the Wenchuan Earthquake area.

Subarea characteristics of earthquake types in Yunnan

Studies on the earthquake sequences and the source mechanisms of the strong earthquakes show that Yurman has more obvious subarea characteristics of earthquake type. Strike-slip seismic fault and mainshock-aftershock earthquake sequences are dominant in whole Yunnan area. Considering the ratio of non strike-slip faults and non mainshock-aftershock, Yurman area can be divided into four subareas with different characteristics, which are strike-slip mainshock-aftershock in central Yunnan （A1）, incline-slip swarm in northwestern Yunnan （A2）, strike-slip double shocks in western Yunnan （B1） and quasi-strike-slip mainshock-aftershock in southwestern Yunnan （BE）, respectively.

Vegetation Restoration Monitoring in Yingxiu Landslide Area after the 2008 Wenchuan Earthquake

A total of more than 50000 landslides has occurred in Sichuan province since the"5·12"Wenchuan earthquake,resulting in serious damage to the surface vegetation in southwestern China.In this study,we select Yingxiu,the epicenter of Wenchuan earthquake,as the experimental area.The vegetation coverage information of the experimental area is extracted from the remote sensing images collected in the year of 2005,2011 and 2013,respectively.The surface vegetation coverage in different periods is analyzed,and the vegetation recovery rate of the whole area is calculated.The experimental results show that in the first three years after the earthquake,the speed of vegetation restoration is slow,and the vegetation coverage rate is less than 20%better than 0.241,while in 2013,the vegetation coverage increases significantly.

Co-seismic changes of well water level and volume strain meter in capital area and its vicinity,due to the Nov.14,2001 Ms8.1 Kunlun Mountain earthquake,China

The Kunlunshan Mountain Ms8.1 earthquake, occurred in Nov.14, 2001, is the first event with magnitude more than 8 in the China earthquake monitoring history, specifically at the beginning of digital techniques in precursor monitoring networks. Any investigation of recorded data on this earthquake is very important for testing the operation of the digital monitoring networks and understanding the preparation, occurrence, and adjustment of stress/strain of strong continental earthquakes. In this paper we investigated the coseismic response changes of well water level of groundwater and volume strain meter of bore hole in digital earthquake monitoring network of Capital area and its vicinity, due to the Nov.14, 2001 Ms8.1 Kunlun Mountain earthquake. The responding time, shapes or manners, amplitudes, and lasting time of well water level and strain-meters to seismic wave are studied in comparison. Then we discussed the possibility that the response changes of groundwater to strong distant earthquakes can be understood as one kind of observing evidence of stress/strain changes induced by distant earthquake.

Territorial suitability assessment and function zoning in the Jiuzhaigou earthquake-stricken area

An earthquake in the Jiuzhaigou area caused numerous secondary disasters, such as rolling stones, land collapse, landslides and debris flow, which badly affected the safety of human settlements and influenced the spatial layout of the post-disaster reconstruction. Therefore, carrying out assessments of land and identifying a suitable zone for human habitats were very important. This research creates the territorial suitability assessment and function zoning conceptual model in the earthquake-stricken area, and the new methods of the territorial suitability evaluation system were used to divide the spatial functional zones of the earthquake stricken area, which provide a theoretical guidance and decisionmaking basis for the reconstruction of the disaster area. The results showed that:(1) The Jiuzhaigou earthquake-stricken area comprises of an ecological area that has a high level of importance to the ecosystem. In the earthquake-stricken area, 65% of national land is at an altitude of 3000-4000 m, and therefore not suitable for a high level of intensive reconstruction, but reconstructed in an eco-friendly manner.(2) The zone suitable for reconstruction comprises mainly of the river valley and the flat terrain of western parts. The land with low suitability is mainly located on steep terrain, such as highmountains and low gullies. The geographic and geomorphic conditions limit the spread of a suitable reconstruction zone.(3) The earthquake-stricken area mainly comprises of a tourism industry gathering area, population gathering area, agriculture and animal husbandry development area, and ecological preservation area with areas of 76 km^2, 44 km^2, 1591 km^2 and 7512 km^2, respectively. Scientifically zoning the reconstruction areas using scientific evaluation may provide guidance for the location of reconstruction sites.

Study of the Seismicity of Strong Earthquakes in the Yunnan Area

Yunnan is located in the east margin of the collision zone between the India Plate and the Eurasian Plate on the Chinese Continent, where crustal movement is violent and moderatestrong earthquakes are frequent. In addition, the area features marked active block movement. Therefore, Yunnan is a perfect place for research on strong earthquake activity. Through the study on the temporal and spatial distribution of the M ≥ 6.7 earthquakes and the related earthquake dynamics in Yunnan in the last century, we conclude that the four seismically active periods, which are characterized by alternative activity in the east and the west part of Yunnan, possibly result from a combination of active and quiescent periods in each of the east and west part. And for every 100 years, there may be a period in which strong earthquakes occur in the east and west parts simultaneously. In addition, the seismicity of strong earthquakes in Yunnan corresponds well to that in the peripheral region. The seismicity of the great earthquakes in the Andaman-Myanmar Tectonic Arc belt indicates, to some extent, the beginning of a seismically active period in Yunnan. The seismicity of strong earthquakes in east Yunnan is closely related to that in Sichuan. Strong earthquakes in Sichuan often occur later than those in Yunnan. Furthermore, in the east part of Ynnnan, the three procedures including continuous occurrence of moderate-strong earthquake, quiescent period, and the occurrence of the first strong earthquake may be the style of the beginning of the earthquake active period. The above cognition is helpful to the study of earthquake prediction, seismogenic mechanism, and the dynamics of the plate margin in Yunnan.

Relocation of Earthquakes in the Northeastern Tianshan Mountains Area and Improvement of Local 1-D Crustal Velocity Model

We apply three methods to relocate 599 earthquake events that occurred from August 2004 to August 2005 in the northeastern Tianshan Mountains area ( 85°30' ～ 88°30'E,43°00' ～ 44°40' N ) by using travel times recorded by regional seismic network and 10 portable seismic stations deployed around the Urumqi city. By comparing the reliability of different results,we determined a suitable location method,and an improved 1-D crustal velocity model of the study area. The uncertainty of earthquake location is significantly reduced with combined data of seismic network and portable stations. The relocated events are clearly associated with regional tectonics of the northeastern Tianshan Mountains area, and are also in agreement with the existence of active faults imaged by deep seismic reflection profile. The relocated seismicity discovers some potential traces of buried active faults,which need to be validated further.

The relationship between the earthquakes of Ningbo area and the Neotectonic movement

On the basis of analysis of historic earthquakes, seismicity, Neotectonics and fault activity in Ningbo area, we estimate its seismotectonic environment and evaluate its seismic risk. This study gives an example of engineering seismology in weak seismicity areas of the eastern part of China.

Several Typical Geomechanical Models of Deformation Fracture of Mountain in High Earthquake Intensity Area

The deformation fracture and stability of mountain under the earthquake action is an important issue that arouses concern of researchers in the field of engineering geology.The authors,from 2000 to 2006, selected the 1933 earthquake in Diexi zone as a typical study site to carry out the genetic mechanism research of mountain deformation-fracture caused by earthquake; in order to have comparability,the breadth

Tectonic environment and cause of earthquakes in the Three Gorges reservoir area

Seismotectonics in the Three Gorges reservoir area is investigated by using the P-wave tomography with earthquakes that occurred before the impoundment of the reservoir. The result indicates that most of these events occurred in or around the velocity-gradient belts between high-velocity and low-velocity anomalies. These belts have similar characteristics to buried-fauh zones. Stresses generated by movement of partially molten upper-mantle materials and thermal stress may have jointly contributed to the seismic activities along the faults and such buried faults, and possibly activated new earthquake ruptures.

Moment tensor inversion and source rupture process of the September 27, 2003 M_S=7.9 earthquake occurred in the border area of China, Russia and Mongolia

plane with the strike of 127°, the dip of 79° and the rake of 171°. The rupture process inversion result of MS=7.9 earthquake shows that the total rupture duration is about 37 s, the scalar moment tensor is M0=0.97 × 1020 N·m. Rupture mainly occurred on the shallow area with 110 km long and 30 km wide, the location in which the rupture initiated is not where the main rupture took place, and the area with slip greater than 0.5 m basically lies within 35 km deep middle-crust under the earth surface. The maximum static slip is 3.6 m. There are two distinct areas with slip larger than 2.0 m. We noticed that when the rupture propagated towards northwest and closed to the area around the MS=7.3 hypocenter, the slip decreased rapidly, which may indicate that the rupture process was stopped by barriers. The consistence of spatial distribution of slip on the fault plane with the distribution of aftershocks also supports that the rupture is a heterogeneous process owing to the presence of barriers.