Impact of intensity and loss assessment following the great Wenchuan Earthquake

The great Wenchuan Earthquake occurred on May 12, 2008 in the Sichuan Province of China, and had a magnitude of 8.0. It is the most serious earthquake disaster in China since the great Tangshan Earthquake （Ms=7.8, July 28, 1976）. According to official reports, there were 69,225 deaths, 379,640 injuries and 17,939 missing as of Aug. 11, 2008. The China Earthquake Administration quickly sent hundreds of experts to the field immediately after the event, to investigate the damage and assess the economic losses. This paper emphasizes the impact of seismic intensity and presents a preliminary loss assessment. A brief description of the geological features of the affected region is provided, followed by a summary of the earthquake damage. An isoseismal map is developed that shows that the high intensity region is distributed like a belt around the seimogenic fault, and that the epicentral intensity reached Ⅺ （Chinese Intensity Scale, similar to the Modified Mercalli Scale）. The direct economic loss resulting from the earthquake is 692 billions RMB （about 100 billions US$）.

Evaluation model of landslide hazards induced by the 2008 Wenchuan earthquake using strong motion data

Landslides induced by the 2008 Wenchuan earthquake in the Longmenshan area were relatively well instrumented, which makes it possible to investigate the landslides using ground motion records. Firstly, this paper analyzes the data from Wenchuan earthquake on both regional and local site scale. The analyses show that the Newmark accumulative displacement calculated from the ground motion recorded in a particular geological hazard zone corresponds to the hazard intensity in that zone; the larger the displacement, the more serious the geologic hazard. The calculated result also shows that the displacement is related to the Arias intensity, which represents the total energy released during the earthquake at the observation site. Secondly, this paper constructs an evaluation model of Newmark displacement calculated with Arias intensities to estimate the subsequent slope failure resulting from the earthquake. The calculated results based on the model fit well with the distribution of actual landslides, suggesting that this method is useful for hazard evaluation. Therefore, this type of model can be used for estimating regional-scale distribution of earthquake-induced landslides and their associated hazards immediately after an earthquake.

Performance of the Yangbi M_(S)6.4 earthquake disaster in different geomorphic units in Yunnan

An M_(S)6.4 earthquake occurred in Yangbi,Yunnan province,on May 21,2021.According to related investigations,the macro-epicenter of the earthquake is 6 km northwest of Yangbi County,and the seismogenic structure is the NW-trending Weixi-Qiaohou fault.The earthquake area is located in the hinterland of the Hengduan Mountains in the northwest of Yunnan Province,a region dominated by high and medium-high mountains,with deep canyons and tectonic basins in between.Various geomorphic features are derived from drastic topographic changes and huge geological differences in the earthquake area.There are a variety of buildings in the earthquake-affected zone,including civil and brick-wood structures ones with weak seismic performance,as well as brick-concrete and frame ones with better seismic performance.This paper summarizes and analyzes different characteristics of the earthquake in different geomorphic units through field investigations of different buildings and geological disasters in the affected area.The results show that under the same earthquake intensity,the damage to most buildings(located in slope areas or rooted in weak strata)is amplified by the earthquake.The earthquake has exerted an obvious propagation effect along the direction of the seismogenic structure.Moreover,local ground fissures will aggravate the damage to the buildings even without surface dislocation.Thus,we suggest that attention should be paid to the ground fissures caused by the slope effect.The fissure areas may also be the disaster spot of collapses and landslides in case of a high-magnitude earthquake.

The Epi－continental arc of Southeast China and relevant earthquakes

Epi continental arc system is a series of arcuate structures along coastlines of the mainland and behind the island arc system on the margin of the Northwest peri Pacific region. Epi continental arc is similar to the island arc in geometery and kinematics, but it was characterised by an arcuate fracture zone and compensated front sag, basic volcanic activity, shallow earthquake belt and the latest active tectonics. The eastern China continent is dominated by the coastal epi continental arc of Southeast China. Its front arc is situated along the coastline of Zhejiang, Fujian and eastern Guangdong provinces which is convex to SE. The left NW trending flank extended along the NW trending coast line of northern Jiangsu and traversed Shangdong Peninsula to northern Hebei and Shanxi provinces; and the right E W trending flank along the western Guangdong, southern Guangxi, northern Hainan coastlines extended to northern Hanoi. This arc controlls activities of the most modern intense earthquakes in eastern China continents. The compressing thrust type earthquakes occurred along the front arc, especially the 'collison belt', and the strike slip type earthquakes along the both flanks sinistral and dextral strike slip faults respectively. Earthquakes of epi continental arc type is characterised by segmentation in space and periodicity in time.

Rapid estimation of earthquake loss based on instrumental seismic intensity: design and realization

As a result of our ability to acquire large volumes of real-time earthquake observation data, coupled with increased computer performance, near real-time seismic instrument intensity can be obtained by using ground motion data observed by instruments and by using the appropriate spatial interpolation methods. By combining vulnerability study results from earthquake disaster research with earthquake disaster assessment models, we can estimate the losses caused by devastating earthquakes, in an attempt to provide more reliable information for earthquake emergency response and decision support. This paper analyzes the latest progress on the methods of rapid earthquake loss estimation at home and abroad. A new method involving seismic instrument intensity rapid reporting to estimate earthquake loss is proposed and the relevant software is developed. Finally, a case study using the ML4.9 earthquake that occurred in Shun-chang county, Fujian Province on March 13, 2007 is given as an example of the proposed method.

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.

The historic evolution of Zhouyuan and the newest activity of the great Wei River fault

The rate of vertical differential movement of the great Weihe fault (west segment) in different periods is analyzed by using the data of the historic evolution of the Zhouyuan plateau surface. Results show that the rate reached a maximum in the Ming Dynasty, about 6. 4 mm/a, which corresponded well to the period of strongearthquake on the Wei River fault in the 15-16th centuries. Based on such a correspondence, the time separation between active periods of Ms=8. 0 strong earthquakes in the Wei River fault depression is investigated.

Evolution characteristics of seismic intensity in Tangshan seismic zone

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