Rapid Identification and Emergency Investigation of Surface Ruptures and Geohazards Induced by the M_s 7.1 Yushu Earthquake

The rapid identification based on InSAR technology was proved to be effective in our emergency investigation of surface ruptures and geohazards induced by the Yushu earthquake.The earthquake-generating fault of the Yushu earthquake is the Yushu section of the Garze-Yushu faults zone.It strikes NWW-NW,23 km long near the Yushu County seat,dominated by left-lateral strike slip,and appearing as a surface rupture zone.The macroscopic epicenter is positioned at Guo-yang-yan -song-duo of Gyegu Town（33°03＇11＂N,96°51＇26＂E）,where the co-seismic horizontal offset measured is 1.75 m.Geohazards induced by the Yushu earthquake are mainly rockfalls,landslides,debris flows, and unstable slopes.They are controlled by the earthquake-generating fault and are mostly distributed along it.There are several geohazard chains having been established,such as earthquake,canal damage,soil liquefying,landslide-debris flow,earthquake,soil liquefying,roadbed deformation,etc.In order to prevent seismic hazards,generally,where there is a visible surface rupture induced by the Yushu earthquake,reconstruction should be at least beyond 20 m,on each side,from it.Sufficient attention should also be given to potential geohazards or geohazard chains induced by the earthquake.

Risk Assessment of Secondary Geological Disasters Induced by the Yushu Earthquake

The Yushu Ms 7.1 earthquake occurred on April 14,2010 in Qinghai Province,China.It induced a mass of secondary geological disasters,such as collapses,landslides,and debris flows.Risk assessment maps are important for geological disaster prevention and mitigation,and also can serve as a guide for post-earthquake reconstruction.Firstly,a hazard assessment index system of secondary geological disasters in the earthquake region was built in this paper,which was based on detailed analysis of environmental and triggering factors closely related to geological disasters in the study area.GIS technology was utilized to extract and analyze the assessment index.Hazard assessment maps of secondary geological disasters were obtained by spatial modeling and overlaying analysis.Secondly,an analysis of the vulnerability of hazard bearing bodies in the area was conducted,important information,such as, population density,percentage of arable land, industrial and agricultural outputs per unit area were regarded as assessment indices to evaluate socioeconomic vulnerability.Thirdly,the risk level of secondary geological disasters of the area was obtained by the formula:Risk=Hazard×Vulnerability. Risk assessment maps were categorized into four levels,including"low","moderate","high"and"very high".These results show that some urban areas are at very high risk,including Jiegu,Chengwen,Xiaxiula and Sahuteng towns.This research can provide some references and suggestions to improve decisionmaking support for emergency relief and post- earthquake reconstruction in the study area.

Gravity changes before and after the 2010 Ms7.1 Yushu earthquake

Absolute and relative gravity observations from 1998 -2010 from the China Crustal Movement Ob- servation Network, a major national scientific project, have been used to model the gravity field and its varia- tions associated with the April 14, 2010 Ms7.1 Yushu earthquake. The evolution of the regional gravity field and its relationship with seismicity before and after the Yushu earthquake are studied. The observed gravity changes are closely related to the active Ganzi-Yushu Fault, and gravity measurements can be used to observe the migration of material accompanying active faults and crustal tectonics. The dynamic variation of the gravity field reflects its evolution prior to and during the Yushu earthquake. The gravity measurements near its epicen- ter are as large as 80 × 10-s m/s2.and they show wave-like increases with time prior to the Yushu earth- quake.

A successful mountain rescue operation in Yushu Earthquake

On April 14, 2010, an earthquake reaching 7.1 Richter scale struck Jiegu Town of Yushu. More than 2 698 people were confirmed dead, and 12 135 were injured, of which 1 434 were severely injured. Rescue operation was carried out soon after the disaster; however, the rescue teams face great challenges of altitude hypoxia, freezing temperature and very bad weather. Thus, 1 434 severe injuries were rapidly transported airlifted to hospitals in Xining and neighboring provinces for effective treatment. The extremity trauma （49.9 % ） was the most common patteru of injuries. Asphyxia （40.8 % ） was by far the most important reason for death. A high incidence of acute altitude illness in the lowland rescuers was a special medical problem during the highest earthquake in Yushu. We have learned more lessons from Yushu Earthquake.

Medical mountain rescue in the Yushu Earthquake: Have lessons been learned?

On April 14,2010,an earthquake reaching Richter scale 7.1 struck Jiegu Town of Yushu,a mountain rescue operation promptly launched. All injurers had a direct assess to take medical care,and were immediately rescued and rapidly evacuated by air to Xining and Golmud at lower altitudes and admitted to advanced hospitals. Almost all of the injurers have been completely recovered. Yushu Earthquake was one of the highest earthquakes in the world,with a high incidence of acute altitude illness,which was observed in about 80 % of the lowland rescuers at an altitude of 4 000 m."Rescue the rescuers"became the major task of Qinghai-Tibetan rescue teams,all the severe patients were rapidly descended to Xining and treated promptly and effectively. The outcome was excellent,all patients survived. After the earthquake,it is a long and arduous task to reconstruct what has been destroyed. Medical teams continue to work in the Yushu Earthquake area because about 30 000 workers and carders are now here for rebuilding the earthquake center. Thus the prevention and treatment of altitude illness are still critical tasks for medical teams. Although all the fights are successful,there are more experiences and lessons we have learned from the medical mountain rescue during the earthquake and the reconstruction,and reports here are to sum up our experiences from the medical mountain rescue operation in Yushu Earthquake and draw the lessons that we should learn. With the increasing of earthquake probability occurring in the Qinghai-Tibetan Plateau,we also should prepare against earthquake disasters and for further rescue training in the high mountains.

Ascent schedules,acute altitude illness,and altitude acclimatization:Observations on the Yushu Earthquake

During the Yushu Earthquake on April 14,2010,a large number of rescuers from sea level or lowlands ascended to the quake areas very rapidly or rapidly less than 24 h. However,Yushu Earthquake is the highest quake in the world at altitudes between 3 750 m and 4 878 m where is a serious hypoxic environment. A high incidence of acute altitude illness was found in the unacclimatized rescuers;the mountain rescue operation changed as "rescue the rescuers". Lesson from the Yushu Earthquake is that the occurrence of acute altitude illness may be closely related to the ascent schedules. This prompted us to study the relationship between ascent rate and the incidence and severity of acute altitude illness;five different groups were compared. The first group was 42 sea level male young soldiers who ascended to quake area very rapidly within 8 h at 4 000 m;the second group was 48 sea level male young soldiers who ascended to 4 000 m rapidly less than 18 h;the third group was 66 acclimatized medical workers from 2 261 m who ascended to 4 000 m rapidly within 12 h;the fourth group was 56 Tibetan medical workers from 2 800 m who ascended to 4 000 m rapidly within 8 h;the fifth group was 50 male sea level workers who ascended to 4 000 m gradually over a period of 4 d. The results showed that the sea level rescuers ascended to 4 000 m very rapidly or rapidly had the highest incidence of acute mountain sickness (AMS) with the greatest AMS scores and the lowest arterial oxygen saturation (SaO2);the sea level workers ascended to 4 000 m gradually had moderate incidence of AMS with moderate AMS scores and SaO2 values;whereas the acclimatized and adapted rescuers had the lowest incidence of AMS,lowest AMS scores and higher SaO2;especially none AMS occurred in Tibetan rescuers. AMS score is inversely related to the ascent rate (r=-0.24,p< 0.001). Additionally,acute altitude illness is significantly influenced by altitude acclimatization. The ascent rate is inversely re- lated to the period of altitude acclimatization whereas the time of perfect recovered from AMS is positively correlated to the time taken to acclimatize. Generally,the best means of preventing acute altitude illness is slow and gradual ascent to high altitude,as this allows time for establishing altitude acclimatization and tolerance to the hypoxic environment. However,during an emergency circumstance,such as mountain rescue operation,the rescuers must rapidly ascend to high altitude,so a series of preventive strategies including pre-acclimatization,using some prophylactic drugs and oxygen supplementary are sorely necessary.

A necklace of pearl in high altitude medicine and hypoxic physiology in Yushu Earthquake

During Yushu Earthquake,a large number of rescuers flocked to the mountainous quake areas. Under such a very specific circumstance,a high incidence of acute altitude illness was observed in rescuers who rapidly traveled from near sea level to an altitude of 4 000 m. It is evident that acute altitude illness leads to a significant human and economic toll,and also seriously influences the mountain rescue operation. So what does this teach us about mountain rescue in Yushu? Professor Wu Tianyi and many other authors collected shining points of the experiences and drew the lessons from the Yushu Earthquake into this special issue in Engineering Sciences which is like to thread pearl beads for a necklace. What readers learn from this special issue will have implications for the health and well-being of all high altitude populations all over the world.

Co-seismic deformation of the 2010 Mw6. 9 Yushu earthquake from InSAR images

Co-seismic ground-surface deformation of the Yushu earthquake on April 14, 2010 is studied on the basis of interferometry principle by using InSAR images from ALOS PALSAR and ENVISAT ASAR pairs. The observed maximum line-of-sight displacement is 54 cm, which is equivalent to a sinistral strike slip of 180 cm on the surface. The location of macro-epicenter is very close to the epicenter determined by in situ investigation, suggesting that InSAR is an ideal tool for quick identification of the macro-epicenter, and thus for timely disaster assessment after a destructive earthquake.

Landslides and Slope Fissures Triggered by the April 14,2010 Yushu Earthquake, China

On April 14, 2010 at 07：49 （Beijing time）, a catastrophic earthquake with Ms 7. 1 occurred at the central Qinghai-Tibetan Plateau. The epicenter was located at Yushu county, Qinghai Province, China. A total of 2036 landslides were determined from visual interpretation of aerial photographs and high resolution remote sensing images, and verified by selected field investigations. These landslides covered a total area of about 1. 194km~. Characteristics and failure mechanisms of these landslides are listed in this paper, including the fact that the spatial distribution of these landslides is controlled by co- seismic main surface fault ruptures. Most of the landslides were small scale, causing rather less hazards, and often occurring close to each other. The landslides were of various types, including mainly disrupted landslides and rock falls in shallows and also deep-seated landslides, liquefaction induced landslides, and compound landslides. In addition to strong ground shaking, which is the direct landslide triggering factor, geological, topographical, and human activity also have impact on the occurrence of earthquake triggered landslides. In this paper, five types of failure mechanisms related to the landslides are presented, namely, the excavated toes of slopes accompanied by strong ground shaking; surface water infiltration accompanied by strong ground shaking; co- seismic fault slipping accompanied by strong ground shaking; only strong ground shaking; and delayed occurrence of landslides due to snow melt or rainfall infiltration at sites where slopes were weakened by co-seismic ground shaking. Besides the main co-seismic surface ruptures, slope fissures were also delineated from visual interpretation of aerial photographs in high resolution. A total of 4814 slope fissures, with a total length up to 77. lkm, were finally mapped. These slope fissures are mainly distributed on the slopes located at the southeastern end of the main co-seismic surface rupture zone, an area subject to strong compression during the earthquake.

Imaging manifestations and the related clinical characteristics of chest trauma during the Yushu Earthquake

The purpose of this study was focused on the imaging features of the chest trauma and its relation to clinical characteristics. All the injured patients were from the Yushu Earthquake areas on days April 14 - 23,2010. After an initial treatment,the injurers were rapidly transported from Yushu at an altitude of 4 000 m via air to Xining at 2 260 m within 6~8 h,and promptly admitted to Qinghai Provincial People’s Hospital. A total of 130 wounded injurers who had high suspicion of chest injuries all had examinations of Chest X-ray and computed tomography(CT)images. Of them 63 injurers presented at least one of the features of the chest trauma in imaging with a positive rate of 48.5 %. Of these,37 cases (28.5 %) were multi-system with multiple injuries ,33 cases (25.4 %) were chest trauma with multi-injury types,which included thoracic fractures in 54 cases (85.7 %),pleural injury in 56 cases (88.9 %),lung injury in 54 cases (85.7 %),lungs complications in 37 cases (58.7 %),and extrapulmonary complications of 35 cases (55.6 %). The radiological data were analyzed retrospectively. The features of chest trauma in Yushu Earthquake,the complications of chest injuries,and the relation between imaging findings and clinical manifestations,as well as the differences of chest trauma between Yushu Earthquake and Wenchuan Earthquake were discussed in detail.

Surface Rupture and Coseismic Displacement of the M_S7.1 Yushu Earthquake

On April 14, 2010, a devastating earthquake measured 7.1 on the Richter scale struck Yushu county, Qinghai Province, China. Field geological investigation and remote sensing interpretation show that this earthquake generated an inverse ＂L-shaped＂ surface rupture zone, approximately 50km long. The surface rupture zone can be divided into three segments. Between the northern and middle segments of the surface rupture, there is a 16km-long segment, where no rupture was observed. The middle and the southern segments are arranged in a left-step manner, and there are right-step en echelon ruptures developed in the stepovers. The seismogenic structure is the Yushu fault, which is dominated by strike-slip with a small amount of thrust component. The earthquake results from the differential movements between the southern Qiangtang Block and northern Bayan Har Block. The earthquake recurrence interval is 185a^108a. Along an approximately 20km-long part of the Garze-Yushu fault, between the southern surface rupture of Yushu Ms7. 1 earthquake and the 1896 earthquake, there is no surface rupture, its seismic risk needs further research.

A Study on the Characteristics of Anomalies and Their Dynamic Relationship before the April 14, 2010 M_S 7.1 Yushu Earthquake

The authors studied the seismic activity, precursory anomalies and abnormal animal behavior before the April 14, 2010 Ms 7.1 Yushu earthquake. Analysis showed that anomalies were not rich before the Ms 7.1 Yushu earthquake, but prominent anomalies were observed, such as the long and mid-term trend anomaly characterized by the seismic quiescence of Ms6. 0, MsS. 0 and Ms4.0 earthquakes, and the anomalies in precursor observation of surface water temperature in Yushu and Delingha and electromagnetic measurement in Ping＇an. There were a large number of animal behavior anomalies appearing one week before the earthquake. An M4.7 earthquake occurred 130 minutes before the main shock. In this paper, we studied the dynamic process of the Yushu earthquake preparation using the earthquake focal mechanism solutions on the Bayan Har block boundary since 1996. The results show that the Kalakunlun M7.1 earthquake in 1996, the Mani M7.5 earthquake and the Yushu Ms7.1 earthquake have the same dynamic process. Long and mid-term trend anomalies may be related to the dynamics of evolution of different earthquakes. This paper also discusses the recurrence interval of strong earthquakes, foreshock identification and precursor observation of the Yushu Ms7. 1 earthquake.

The Effect of Static Stress Triggering of the M_S 7. 1 Yushu Earthquake

This paper calculates the static stress changes generated by the Yushu M_S 7. 1 earthquake in Qinghai Province. On the basis of regional stress,we take account of the static stress change triggered by the Yushu M_S 7. 1 earthquake to find the optimally oriented fault planes,then calculate the Coulomb stress change on the optimally oriented fault plane. The results indicate that most of the aftershocks are triggered by the mainshock. The image of Coulomb stress changes is also in accord with regional earthquakes ( M_L ≥3. 0 ) distribution,but the value is lower than 0. 01MPa. In addition,this paper calculates the Coulomb stress changes in the case that the aftershock fault plane is the same as the main shock. Through comparison,we find that the image of Coulomb stress changes obtained using the "optimally oriented fault"approach is more consistent with the distribution of Yushu aftershocks and regional earthquakes.

The Emergency Scientific Investigation on the Surface Rupture Zone of the M_S 7.1 Yushu Earthquake

The coseismic surface rupture zone of the seismogenic fault of the Ms7.1 Yushu earthquake includes three left-stepping main ruptures, striking 300°- 320°, in general. An approximately 2km-long en echelon tension fissure zone was found at Longbao town. The main rupture in the northern part is about 16km long, about 9kin long in the middle part, and about 7km long in the southern part, with a total length of 34km. Each of the main ruptures consists of a series of en echelon sub-ruptures represented by a series of compression bulges alternating with tension fissures or by en echelon fissures. The rupture at Changusi, the southernmost of the ruptures, is characterized by vertical displacement, with a value of 50cm. The rupture zone shows left-lateral strike-slip characteristics. The maximal horizontal slip is on the northern main rupture, with a value of 1.8m.

Analysis of CHARTER Applied for Yushu Earthquake Relief

Natural disasters are common threats to all human beings. With the background of global climate change, major natural disasters have occurred frequently in the last few years and caused heavy casualties with high property losses. Satellite Earth ob-servation has been playing a more and more important role in monitoring

The April 14th, 2010 Yushu earthquake, a devastating earthquake with foreshocks

In the early morning of April 14th, 2010, a strong earth- quake (Ms7.1, http://www.csndmc.ac.cn; Mw6.9, http://neic. usgs.gov) occurred in Yushu district, Qinghai Province, China. More than 2000 lives were lost and over 100000 injured,

Correcting ionospheric effects and monitoring two-dimensional displacement fields with multiple-aperture InSAR technology with application to the Yushu earthquake

Differential synthetic aperture radar interferometry (D-InSAR) can only measure one-dimensional surface displacements along the line-of-sight (LOS) direction which greatly inhibits its development and application.In this paper, we introduce a novel approach to measuring two-dimensional (2-D) surface displacements by exploiting a single InSAR pair, which is called multi-aperture InSAR (MAI) technology.We study the effects of baseline errors and the ionosphere on MAI technology and develop a directional filter and interpolator to minimize the ionospheric effects.A PALSAR image pair covering the 2010 Yushu earthquake is used to estimate the 2-D displacement fields of the earthquake using the MAI approach.The experimental results show that MAI is superior to conventional Offset-Tracking and therefore has great potential in co-seismic displacement measurement and source parameter inversion.

Seismic relocation,focal mechanism and crustal seismic anisotropy associated with the 2010 Yushu M_S7.1 earthquake and its aftershocks

The 2010 Yushu MsT.1 earthquake occurred in Ganzi-Yushu fault, which is the south boundary of Bayan Har block. In this study, by using double difference algorithm, the locations of mainshock （33.13°N, 96.59°E, focal depth 10.22 km） and more than 600 aftershocks were obtained. The focal mechanisms of the mainshock and some aftershocks with Ms〉3.5 were estimated by jointly using broadband velocity waveforms from Global Seismic Network （GSN） and Qinghai Seismic Network as well. The focal mechanisms and relocation show that the strike of the fault plane is about 125° （WNW-ESE）, and the mainshock is left-laterally strikeslip. The parameters of shear-wave splitting were obtained at seismic stations of YUS and L6304 by systematic analysis method of shear-wave splitting （SAM） method. Based on the parameters of shear-wave splitting and focal mechanism, the characteristics of stress field in seismic source zone were analyzed. The directions of polarization at stations YUS and L6304 are different. It is concluded that after the mainshock and the Ms6.3 aftershock on April 14, the stress-field was changed.

Modeling of co- and post-seismic surface deformation and gravity changes of M W 6.9 Yushu, Qinghai,earthquake

Based on the elastic dislocation theory, multilayered crustal model, and rupture model obtained by seismic waveform inversion, we calculated the coand post-seismic surface deformation and gravity changes caused by the Yushu M W 6.9 earthquake occurred on April 14, 2010. The observed GPS velocity field and gravity field in Yushu areas are disturbed by the coand post-seismic effects induced by Yushu earthquake, thus the theoretical coand post-seismic deformation and gravity changes will provide important modification for the background tectonic movement of Yushu and surrounding regions. The time relaxation results show that the influences of Yushu earthquake on Yushu and surrounding areas will last as long as 30 to 50 years. The maximum horizontal displacement, vertical uplift and settlement are about 1.96, 0.27 and 0.16 m, respectively, the maximal positive and negative value of gravity changes are 8.892×10-7 m·s-2 and -4.861×10-7 m·s-2 , respectively. Significant spatial variations can be found on the coand post-seismic effects： The co-seismic effect mainly concentrates in the region near the rupture fault, while viscoelastic relaxation mostly acts on the far field. Therefore, when using the geodetic data to research tectonic motion, we should not only consider the effect of co-seismic caused by earthquake, but also pay attention to the effect of viscoelastic relaxation.

Estimating Moho basement and faults using gravity inversion in Yushu-earthquake area,China

A gravity survey was conducted one month after the 2010 Yushu earthquake in the epicenter area. The cross-fauh survey line was 500 km long, from Langqian county to Qingshuihe county, in a transition zone between Bayan Har block and Qiangtang block, in an area of high elevation, large undulating terrain, and complex geological features. An interpretation of the data was carried out together with other kinds of data, such as seismic exploration and magnetic exploration. The result shows that gravity is sensitive to fault bounda- ry ; the geologic structure of the region is complex at middle and upper depths, and the density profile reveals an eastward-pushing fault movement.