Home About us Contact
|
Home About us Contact | ||
|
|
||
Earthquake
Kinds of Earthquake Terms modified by Earthquake Selected AbstractsMONITORING SYSTEM PROVES ROOFTOP SAFE AFTER SEATTLE EARTHQUAKEEXPERIMENTAL TECHNIQUES, Issue 3 2001Vincent P. Wnuk No abstract is available for this article. [source] OUTBREAK OF NOROVIRUS GASTROENTERITIS IN ELDERLY EVACUEES AFTER THE 2007 NOTO PENINSULA EARTHQUAKE IN JAPANJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 2 2008Koji Nomura MD No abstract is available for this article. [source] THE LIGHTNING AND THE EARTHQUAKE: KIERKEGAARD ON THE ANFECHTUNG OF LUTHERTHE HEYTHROP JOURNAL, Issue 4 2006SIMON D. PODMORE By focusing discussion through Søren Kierkegaard's view of Martin Luther's initiation into the monastery (the lightning strike), it is suggested that an analogy can be discerned for Kierkegaard's own sense of divine vocation (the portentous ,earthquake' which he makes enigmatic reference to) and the ensuing self-mortification of melancholy and religious scrupulosity which commentators have suspected in both figures. Kierkegaard's often ambivalent critique of Luther's Anfechtung is thus read as bearing ironic significance for his own struggles with ,spiritual trial' [Anfægtelse]. In this reading, Luther's Anfechtung is taken to signify for Kierkegaard both the anguish inherent to the authentic God-relationship and also the dangerous possibility of the individual imagination's [Phantasi] capitulation into the precariously embellished realm of ,the fantastic' [Phantastiske]. It is here that Kierkegaard's emphasis upon individual responsibility , contrasted with Luther's concentration upon the role of the devil , demonstrates the fundamental differentiation between Kierkegaard's anatomy of Anfægtelse and Luther's Anfechtung. [source] Civil Society and the State: Turkey After the EarthquakeDISASTERS, Issue 2 2002Rita Jalali On 17 August 1999 Turkey was hit by a massive earthquake. Over 17,000 lives were lost and there was extensive damage to Turkey's heartland. This paper examines how various public and private institutions, including state and civil society institutions such as NGOs and the media responded to the needs of earthquake survivors. It documents the extensive involvement of NGOs in the relief efforts immediately after the disaster and examines the impact of such participation on state-civil society relations in the country. The data show that state response to the disaster went through several phases from a period of ineptitude to effective management. The paper credits the media and the NGOs for acting as advocates for survivors and forcing changes at the state level. The paper argues that an ideal response system, which fully addresses the needs of victims, can only be based on state-civil society relations that are both collaborative and adversarial. [source] Expected loss-based alarm threshold set for earthquake early warning systemsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2007Iunio Iervolino Abstract Earthquake early warning systems (EEWS) seem to have potential as tools for real-time seismic risk management and mitigation. In fact, although the evacuation of buildings requires warning time not available in many urbanized areas threatened by seismic hazard, they may still be used for the real-time protection of critical facilities using automatic systems in order to reduce the losses subsequent to a catastrophic event. This is possible due to the real-time seismology, which consists of methods and procedures for the rapid estimation of earthquake features, as magnitude and location, based on measurements made on the first seconds of the P -waves. An earthquake engineering application of earthquake early warning (EEW) may be intended as a system able to issue the alarm, if some recorded parameter exceeds a given threshold, to activate risk mitigation actions before the quake strikes at a site of interest. Feasibility analysis and design of such EEWS require the assessment of the expected loss reduction due to the security action and set of the alarm threshold. In this paper a procedure to carry out these tasks in the performance-based earthquake engineering probabilistic framework is proposed. A merely illustrative example refers to a simple structure assumed to be a classroom. Structural damage and non-structural collapses are considered; the security action is to shelter occupants below the desks. The cost due to a false alarm is assumed to be related to the interruption of didactic activities. Results show how the comparison of the expected losses, for the alarm-issuance and non-issuance cases, allows setting the alarm threshold on a quantitative and consistent basis, and how it may be a tool for the design of engineering applications of EEW. Copyright © 2007 John Wiley & Sons, Ltd. [source] Experimental study of the semi-active control of building structures using the shaking tableEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 15 2003Qing Sun Abstract A magnetorheological (MR) damper has been manufactured and tested and a non-linear model is discussed. The parameters for the model are identified from an identification set of experimental data; these parameters are then used to reconstruct the force vs. displacement and the force vs. velocity hysteresis cycles of the MR damper for the hysteretic model. Then experiments are conducted on a three-storey frame model using impact excitation, which identifies dynamic parameters of the model equipped with and without the MR damper. Natural frequencies, damping ratios and mode shapes, as well as structural properties, such as the mass, stiffness and damping matrices, are obtained. A semi-active control method such as a variable structure controller is studied. Based on the ,reaching law' method, a feedback controller is presented. In order to evaluate the efficiency of the control system and the effect of earthquake ground motions, both numerical analysis and shaking table tests of the model, with and without the MR damper, have been carried out under three different ground motions: El Centro 1940, Taft 1952, and Ninghe 1976 (Tangshan Earthquake in Chinese). It is found from both the numerical analysis and the shaking table tests that the maximum accelerations and relative displacements for all floors are significantly reduced with the MR damper. A reasonable agreement between the results obtained from the numerical analysis and those from the shaking table tests is also observed. On the other hand, tests conducted at different earthquake excitations and various excitation levels demonstrate the ability of the MR damper to surpass the performance of a comparable passive system in a variety of situations. Copyright © 2003 John Wiley & Sons, Ltd. [source] Globalizing Disaster Trauma: Psychiatry, Science, and Culture after the Kobe EarthquakeETHOS, Issue 2 2000Joshua Breslau In January of 1995 a massive earthquake struck the city of Kobe, Japan. This article examines how this event became an opportunity for extending global networks of the science and medicine of trauma. The article is based on ethnographic research in Kobe and Los Angeles with psychiatrists who responded to the earthquake in its immediate aftermath. Three aspects of the process are examined: 1) changes in psychiatric institutions that were ongoing at the time of the earthquake, 2) the place of psychiatry in Japanese cultural self-criticism, and 3) the particular technologies for identifying and treating trauma. Globalization in this case cannot be seen as an imposition of Western cultural forms, but rather an ongoing process that reproduces differences between cultures as particular elements travel between them. [source] A cyclic viscoelastic,viscoplastic constitutive model for clay and liquefaction analysis of multi-layered groundINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 2 2004Fusao Oka Abstract In order to estimate viscous effect of clay in the wide range of low to high level of strain, a cyclic viscoelastic,viscoplastic constitutive model for clay is proposed. First, we confirm the performance of the proposed model by simulating the cyclic undrained triaxial tests to determine the cyclic strength and deformation characteristics of a natural marine clay. Then, the proposed model is incorporated into an effective stress based liquefaction analysis method to estimate the effect of an intermediate clay layer on the behaviour of liquefiable sand layers. The seismic response against foreshocks, main shock as well as aftershocks of 1995 Hyogoken Nambu Earthquake is analysed in the present study. The difference of shear strength characteristics of the alluvial clay layer is one of the reasons why Port Island has a higher liquefaction potential than that of Rokko Island. The proposed model gives a good description of the damping characteristics of clay layer during large earthquakes. Acceleration responses in both clay layer and liquefiable sand layer just above it are damped due to viscous effect of clay. In the case of main shock and the following aftershocks that occurred within less than 9 days after main event, acceleration responses near ground surface are de-amplified due to the developed excess pore water pressure, while responses near ground surface are amplified before and long after the main event. Using the viscoelastic,viscoplastic model for clay layer, time history of acceleration response in upper liquefiable sand layer can be well calculated, in particular in the range of microtremor process after the main seismic motion. Copyright © 2004 John Wiley & Sons, Ltd. [source] In situ stress measurements in a borehole close to the Nojima FaultISLAND ARC, Issue 3-4 2001Hiroaki Tsukahara AbstractIn situ stress was measured close to the fault associated with the 1995 Kobe Earthquake (Hyogo-ken Nanbu earthquake; January 1995; M7.2) using the hydraulic fracturing method. The measurements were made approximately 2 years after the earthquake. The measured points were approximately 40 m from the fault plane at depths of about 1500 m. The maximum and the minimum horizontal compressive stresses were 45 MPa and 31 MPa, respectively. The maximum compressive stress and the maximum shear stress are very small in comparison with those of other seismically active areas. The azimuth of the maximum horizontal compressive stress was estimated from the observed azimuths of well bore breakouts at depths between 1400 m and 1600 m and was found to be N135° (clockwise). The maximum stress axis is perpendicular to the fault strike, N45°. These features are interpreted in terms of a small frictional coefficient of the fault. The shear stress on the fault was released and dropped almost to zero during the earthquake and it has not yet recovered. Zero shear stress on the fault plane resulted from the perpendicular orientation of one of the principal stress to the fault plane. [source] KeyGraph as Risk Explorer in Earthquake,SequenceJOURNAL OF CONTINGENCIES AND CRISIS MANAGEMENT, Issue 3 2002Yukio Ohsawa KeyGraph, a document,indexing (keyword,extraction) algorithm, is applied for a new purpose: Extracting active faults with risks of near,future large earthquakes from earthquake,sequences. This paper presents KeyGraph as an extractor of causalities from an event,sequence. This validates KeyGraph as a tool for showing why and which active faults are risky, as well as for showing why and which words abstract a document. The risky faults that are empirically obtained by KeyGraph correspond closely to real earthquake occurrences and seismologists' risk estimation. [source] Public Organizations in an Emergency: The 1995 Hanshin-Awaji Earthquake and Municipal GovernmentJOURNAL OF CONTINGENCIES AND CRISIS MANAGEMENT, Issue 1 2000Nobuyuki Hashimoto A magnitude 7.2 earthquake hit one of the major metropolitan areas of Japan at 5:46 am on 17 January 1995. This paper examines the behaviour of public organizations during this event in four municipal governments. Opening and managing shelters, reception of relief goods and cooperation with volunteers are, especially, studied in detail. Some of the programmes implemented by the national government and Hyogo prefectural government are also studied. Based on these studies, characteristics of the organizations' responses during the emergency are analyzed. It is argued that the structure of organizations or the disaster response programmes are formulated or changed by using more stable structures or procedures. [source] Applying lessons from China's Wenchuan earthquake to medical rescue following the Yushu earthquakeJOURNAL OF EVIDENCE BASED MEDICINE, Issue 2 2010Shaolin Deng A 7.1-magnitude earthquake hit China's Qinghai province,4000 meters above sea level, on April 14, 2010, just 702 days after Wenchuan Earthquake. As of 12:00 on April 19, the death toll stood at 1706, with 256 missing and 12,128 injured. West China Hospital (WCH), a regional state-level hospital of the Ministry of Health, sent a medical team with relief supplies within the first hour after Yushu earthquake and the team rushed to Yushu in the first day participating golden seventy-two hours rescue effort. The second day after Yushu earthquake, medical apparatuses and drugs valued at 5 million RMB were delivered to the rescue site and the second batch of medical team were positioned. Within 33 hours of the earthquake, 102 people, including 93 with earthquake-related injuries and 9 armed police with severe altitude sickness, were send to WCH by air in four batches. WCH organized its medical rescue efforts based on first-hand experience with medical rescue following Wenchuan earthquake, a series of evidence-based diagnosis and treatment standards, and "four concentration principles," namely concentrating the wounded, experts, resources, and treatments. Of the 93 cases with earthquake-related injuries, 54 were seriously wounded, and in the five days immediately following the earthquake, 58 underwent operations and none died. The experience learned from Wenchuan earthquake have been used, improved and sublimated more rapidly, appropriately, and effectively in the Yushu earthquake medical rescue. [source] Integrating Transportation Network and Regional Economic Models to Estimate the Costs of a Large Urban EarthquakeJOURNAL OF REGIONAL SCIENCE, Issue 1 2001Sungbin Cho In this paper we summarize an integrated, operational model of losses due to earthquake impacts on transportation and industrial capacity, and how these losses affect the metropolitan economy. The procedure advances the information provided by transportation and activity system analysis techniques in ways that help capture the most important ecomonic implications of earthquakes. Network costs and origin-destination requirements are modeled endogenously and consistently. Indirect and induced losses associated with direct impacts on transportation and industrial capacity are distributed across zones and ecomonic sectors. Preliminary results are summarized for a magnitude 7.1 earthquake on the Elysian Park blind thrust fault in Los Angeles. [source] Derangement of Heart Rate Variability During a Catastrophic Earthquake: A Possible Mechanism for Increased Heart AttacksPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 11 2001LIAN-YU LIN LIN, L.-Y., et al.: Derangement of Heart Rate Variability During a Catastrophic Earthquake: A Possible Mechanism for Increased Heart Attacks. At 1:47 AM on September 21, 1999, the middle part of Taiwan was struck by a major earthquake measuring 7.3 on the Richter scale. It has been shown that the mental stress caused by an earthquake could lead to a short- or long-term increase in frequency of cardiac death probably through activation of the sympathetic nervous system. The aim of this study was to investigate the effects of emotional stress on the autonomic system during an actual earthquake. Fifteen patients receiving a 24-hour Holter ECG study starting from 10 ± 4 hours before the onset of the earthquake were included for the analysis of time- and frequency-domains of heart rate variability (HRV) at several time periods. A 24-hour Holter study recorded 2,6 months before the earthquake in 30 age- and sex-matched subjects served as the control group. Heart rate and the low frequency (LF) to high frequency (HF) ratio increased significantly after the earthquake and were attributed mainly to the withdrawal of the high frequency component (parasympathetic activity) of HRV. Sympathetic activation was blunted in elderly subjects > 60 years old. The concomitant ST-T depression observed in the Holter study correlated with a higher increment of LF as compared to HF components. The changes observed in HRV recovered completely 40 minutes following the earthquake. The derangement of HRV results from the withdrawal of the parasympathetic component and the arousal of sympathetic activity by the stressful earthquake. However, this autonomic derangement returned towards normal 40 minutes following the earthquake. [source] Das Magnitude 8.8 Maule (Chile)-Erdbeben vom 27.BAUTECHNIK, Issue 8 2010Februar 2010, Ingenieuranalyse der Erdbebenschäden Das Maule (Chile)-Erdbeben vom 27. Februar 2010 gehört zu den stärksten, weltweit jemals registrierten Erdbeben. Die Bruchzone erstreckt sich über eine Länge von 500 km und eine Breite von 100 km, so dass acht Millionen Einwohner Chiles von dem Erdbeben mehr oder weniger direkt von den Schütterwirkungen betroffen waren. Bilder von spektakulären Schadensfällen aus der ca. 330 km entfernten Hauptstadt prägten die internationale Berichterstattung. Das seismische Ereignis löste einen Tsunami aus, der verheerende Schäden an der Küste Chiles verursachte und auch an den Küsten Hawaiis noch deutlich wahrgenommen werden konnte. Die seismischen Bodenbewegungen wurden bis ins Nachbarland Argentinien verspürt. Die Stärke des Bebens und ereignisspezifische Besonderheiten waren Motivation, im Rahmen einer Erkundungsmission der Ingenieurgruppe der Deutschen TaskForce Erdbeben im betroffenen Gebiet die Bauwerksschäden aufzunehmen und ihre regionale Verteilung zu dokumentieren. In fünf temporär, mit Starkbeben-Sensoren instrumentierten Gebäuden konnten mehrere Nachbeben aufgezeichnet werden, deren Beschleunigungsamplituden für allgemeine Hochbauten in deutschen Erdbebengebieten von Interesse bzw. maßgeblich wären. Die vorliegenden Messdaten ermöglichen die Interpretation der realen Gebäudereaktion und können in Folgeuntersuchungen zur Kalibrierung analytischer Modelle herangezogen werden. Der Beitrag vermittelt einen Eindruck von den erdbebenbedingten Schäden und soll das Verhalten der typischen Bauweisen unter diesen extremen Einwirkungen aufzeigen, das vor Ort festgestellte geringe Schadensausmaß durch die Umsetzung von Baunormen und darin verankerten Bemessungskonzepten erklären und letztlich die Übertragbarkeit dieser Beobachtungen auf andere Erdbebenregionen hinterfragen. In einem Folgebeitrag [1] werden die Schäden aus dem Tsunami einer Ingenieuranalyse unterzogen und die wesentlichen Wirkungsmechanismen bzw. einfachen baulichen Schutzmaßnahmen herausgearbeitet. The Magnitude 8.8 Maule (Chile) Earthquake of February 27, 2010 , Engineering analysis of earthquake damage. The Maule (Chile) February 27, 2010 Earthquake is regarded as one of the strongest earthquakes ever recorded world-wide. The rupture zone reached a length of about 500 km and a width of about 100 km; almost 8 million inhabitants were directly affected by the consequences of the earthquake. Photos from spectacular failure cases in the Capital (330 km away) were documented across the world and dominated the international reporting. The seismic event triggered a tsunami which caused serious damage alongside the coastal border; the waves were observed in the far-distant Hawaii Islands, too. The seismic ground motions were felt in the neighboring country Argentina, as well. The strength of the earthquake and the event-specific characteristics motivated the "Engineering Group of the German Task Force for earthquake" to analyze the building damage and to document their regional distribution. Five multi-storey RC structures were temporarily equipped with Strong-Motion sensors. Several aftershocks could be recorded; the peak acceleration amplitudes were in a level which was of interest for buildings in highest zone of German earthquake regions. In a first attempt, the measurements are used to interpret the response of real buildings in both horizontal directions; in ongoing studies data are used for the calibration of analytical models. The paper provides an overview of the earthquake induced damages in several building types and its variation within different structural systems. Reasons of low to moderate observed damage will be discussed in close relation to the code development and the preferred design concepts. The application of observed effects and derived lessons to other seismic regions is critically reviewed. In a subsequent paper [1] the damage caused by the tsunami is investigated in more detail. The engineering analysis will include the currently used models for the impact description and will elaborate simple, but quite efficient measures of protection. [source] New Research Results on Mechanism, Surface Rupture, Deep Controlling Factors and Stress Measurements of the Wenchuan Earthquake,Earth Scientists' Post-quake ActionsACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009Shuwen DONG First page of article [source] Parameters of Coseismic Reverse- and Oblique-Slip Surface Ruptures of the 2008 Wenchuan Earthquake, Eastern Tibetan PlateauACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009Xiwei XU Abstract: On May 12th, 2008, the Mw7.9 Wenchuan earthquake ruptured the Beichuan, Pengguan and Xiaoyudong faults simultaneously along the middle segment of the Longmenshan thrust belt at the eastern margin of the Tibetan plateau. Field investigations constrain the surface rupture pattern, length and offsets related to the Wenchuan earthquake. The Beichuan fault has a NE-trending right-lateral reverse rupture with a total length of 240 km. Reassessment yields a maximum vertical offset of 6.5 ± 0.5 m and a maximum right-lateral offset of 4.9 ± 0.5 m for its northern segment, which are the largest offsets found; the maximum vertical offset is 6.2 ± 0.5 m for its southern segment. The Pengguan fault has a NE-trending pure reverse rupture about 72 km long with a maximum vertical offset of about 3.5 m. The Xiaoyudong fault has a NW-striking left-lateral reverse rupture about 7 km long between the Beichuan and Pengguan faults, with a maximum vertical offset of 3.4 m and left-lateral offset of 3.5 m. This pattern of multiple co-seismic surface ruptures is among the most complicated of recent great earthquakes and presents a much larger danger than if they ruptured individually. The rupture length is the longest for reverse faulting events ever reported. [source] Dextral-Slip Thrust Faulting and Seismic Events of the Ms 8.0 Wenchuan Earthquake, Longmenshan Mountains, Eastern Margin of the Tibetan PlateauACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009Zhenhan WU Abstract: Dextral-slip thrust movement of the Songpan-Garzê terrain over the Sichuan block caused the Ms 8.0 Wenchuan earthquake of May 12, 2008 and offset the Central Longmenshan Fault (CLF) along a distance of ,250 km. Displacement along the CLF changes from Yingxiu to Qingchuan. The total oblique slip of up to 7.6 m in Yingxiu near the epicenter of the earthquake, decreases northeastward to 5.3 m, 6.6 m, 4.4 m, 2.5 m and 1.1 m in Hongkou, Beichuan, Pingtong, Nanba and Qingchuan, respectively. This offset apparently occurred during a sequence of four reported seismic events, EQ1,EQ4, which were identified by seismic inversion of the source mechanism. These events occurred in rapid succession as the fault break propagated northeastward during the earthquake. Variations in the plunge of slickensides along the CLF appear to match these events. The Mw 7.5 EQ1 event occurred during the first 0,10 s along the Yingxiu-Hongkou section of the CLF and is characterized by 1.7 m vertical slip and vertical slickensides. The Mw 8.0 EQ2 event, which occurred during the next 10,42 s along the Yingxiu-Yanziyan section of the CLF, is marked by major dextral-slip with minor thrust and slickensides plunging 25°,35° southwestward. The Mw 7.5 EQ3 event occurred during the following 42,60 s and resulted in dextral-slip and slickensides plunging 10° southwestward in Beichuan and plunging 73° southwestward in Hongkou. The Mw 7.7 EQ4 event, which occurred during the final 60,95 s along the Beichuan-Qingchuan section of the CLF, is characterized by nearly equal values of dextral and vertical slips with slickensides plunging 45°,50° southwestward. These seismic events match and evidently controlled the concentrations of landslide dams caused by the Wenchuan earthquake in Longmenshan Mountains. [source] Co-seismic Faults and Geological Hazards and Incidence of Active Fault of Wenchuan Ms 8.0 Earthquake, Sichuan, ChinaACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009Yinsheng MA Abstract: There are two co-seismic faults which developed when the Wenchuan earthquake happened. One occurred along the active fault zone in the central Longmen Mts. and the other in the front of Longmen Mts. The length of which is more than 270 km and about 80 km respectively. The co-seismic fault shows a reverse flexure belt with strike of N45°,60°E in the ground, which caused uplift at its northwest side and subsidence at the southeast. The fault face dips to the northwest with a dip angle ranging from 50° to 60°. The vertical offset of the co-seismic fault ranges 2.5,3.0 m along the Yingxiu-Beichuan co-seismic fault, and 1.5,1.1 m along the Doujiangyan-Hanwang fault. Movement of the coseismic fault presents obvious segmented features along the active fault zone in central Longmen Mts. For instance, in the section from Yingxiu to Leigu town, thrust without evident slip occurred; while from Beichuan to Qingchuan, thrust and dextral strike-slip take place. Main movement along the front Longmen Mts. shows thrust without slip and segmented features. The area of earthquake intensity more than IX degree and the distribution of secondary geological hazards occurred along the hanging wall of co-seismic faults, and were consistent with the area of aftershock, and its width is less than 40 km from co-seismic faults in the hanging wall. The secondary geological hazards, collapses, landslides, debris flows et al., concentrated in the hanging wall of co-seismic fault within 0,20 km from co-seismic fault. [source] Seismogenic Structure around the Epicenter of the May 12, 2008 Wenchuan Earthquake from Micro-seismic TomographyACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009Meijian AN Abstract: A three-dimensional local-scale P -velocity model down to 25 km depth around the main shock epicenter region was constructed using 83821 event-to-receiver seismic rays from 5856 aftershocks recorded by a newly deployed temporary seismic network. Checkerboard tests show that our tomographic model has lateral and vertical resolution of ,2 km. The high-resolution P -velocity model revealed interesting structures in the seismogenic layer: (1) The Guanxian-Anxian fault, Yingxiu-Beichuan fault and Wenchuan-Maoxian fault of the Longmen Shan fault zone are well delineated by sharp upper crustal velocity changes; (2) The Pengguan massif has generally higher velocity than its surrounding areas, and may extend down to at least ,10 km from the surface; (3) A sharp lateral velocity variation beneath the Wenchuan-Maoxian fault may indicate that the Pengguan massif's western boundary and/or the Wenchuan-Maoxian fault is vertical, and the hypocenter of the Wenchuan earthquake possibly located at the conjunction point of the NW dipping Yingxiu-Beichuan and Guanxian-Anxian faults, and vertical Wenchuan-Maoxian fault; (4) Vicinity along the Yingxiu-Beichuan fault is characterized by very low velocity and low seismicity at shallow depths, possibly due to high content of porosity and fractures; (5) Two blocks of low-velocity anomaly are respe tively imaged in the hanging wall and foot wall of the Guanxian-Anxian fault with a ,7 km offset with ,5 km vertical component. [source] Deep Background of Wenchuan Earthquake and the Upper Crust Structure beneath the Longmen Shan and Adjacent AreasACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009Qiusheng LI Abstract: By analyzing the deep seismic sounding profiles across the Longmen Shan, this paper focuses on the study of the relationship between the upper crust structure of the Longmen Shan area and the Wenchuan earthquake. The Longmen Shan thrust belt marks not only the topographical change, but also the lateral velocity variation between the eastern Tibetan Plateau and the Sichuan Basin. A low-velocity layer has consistently been found in the crust beneath the eastern edge of the Tibetan Plateau, and ends beneath the western Sichuan Basin. The low-velocity layer at a depth of ,20 km beneath the eastern edge of the Tibetan Plateau has been considered as the deep condition for favoring energy accumulation that formed the great Wenchuan earthquake. [source] Relationship between Crustal 3D Density Structure and the Earthquakes in the Longmenshan Range and Adjacent AreasACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009Jisheng ZHANG Abstract: This paper presents the 3D density structure of crust in the Longmenshan range and adjacent areas, with constraints from seismic and density data. The density structure of crust shows that the immense boundary plane of density distribution in relation to the Longmeshan fault belt is extended downward to ,80 km deep. This density boundary plane dips towards the northwest and crosses the Moho. With the proximity to the Longmenshan fault belt, it has a larger magnitude of undulation in the upper and middle crust levels. Density changes abruptly across Longmeshan fault belt. Seismic data show that most of the earthquakes in the Longmenshan area after the 2008 Ms8.0 Wenchuan Earthquake occurred within the upper to middle crust. These earthquakes are clearly distributed in the uplifted region of the basement. A few of them occurs in the transitional zone between the uplifted and subsided areas. But most of the earthquakes distributes in transitional zone from subsided to uplifted areas in the upper and middle crust where relatively large density changes occurr The 3D density structure of crust in the Longmenshan and adjacent areas can thus help us to understand the pattern of overthrusting from the standpoint of deep crust and where the earthquakes occurred. [source] Preliminary Results of In-situ Stress Measurements along the Longmenshan Fault Zone after the Wenchuan Ms 8.0 EarthquakeACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009Manlu WU Abstract: Four months after the Wenchuan Ms 8 earthquake in western Sichuan, China, in situ stress measurements were carried out along the Longmenshan fault zone with the purpose of obtaining stress parameters for earthquake hazard assessment. In-situ stresses were measured in three new boreholes by using overcoring with the piezomagnetic stress gauges for shallow depths and hydraulic fracturing for lower depths. The maximum horizontal stress in shallow depths (,20 m) is about 4.3 MPa, oriented N19°E, in the epicenter area at Yingxiu Town, about 9.7 MPa, oriented N51°W, at Baoxing County in the southwestern Longmenshan range, and about 2.6 MPa, oriented N39°E, near Kangding in the southernmost zone of the Longmenshan range. Hydraulic fracturing at borehole depths from 100 to 400 m shows a tendency towards increasing stress with depth. A comparison with the results measured before the Wenchuan earthquake along the Longmenshan zone and in the Tibetan Plateau demonstrates that the stress level remains relatively high in the southwestern segment of the Longmenshan range, and is still moderate in the epicenter zone. These results provide a key appraisal for future assessment of earthquake hazards of the Longmenshan fault zone and the aftershock occurrences of the Wenchuan earthquake. [source] Process Analysis of In-situ Strain during the Ms8.0 Wenchuan Earthquake,Data from the Stress Monitoring Station at ShandanACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009Hua PENG Abstract: There were huge life and property losses during the Ms8.0 Wenchuan earthquake on May 12, 2008. Strain fluctuation curves were completely recorded at stress observatory stations in the Qinghai-Tibet plateau and its surroundings in the process of the earthquake. This paper introduces the geological background of the Wenchuan earthquake and the profile of in-situ stress monitoring stations. In particular, data of 174 earthquakes (Ms4.0,Ms8.5) were processed and analyzed with various methods, which were recorded at the Shandan station from August 2007 to December 2008. The results were compared with other seismic data, and further analyses were done for the recoded strain seismic waves, co-seismic strain stepovers, pre-earthquake strain valleys, Earth's free oscillations before and after the earthquake and their physical implications. During the Wenchuan earthquake, the strainmeter recorded a huge extensional strain of 70 seconds, which shows that the Wenchuan earthquake is a rupture process predominated by thrusting. Significant precursory strain anomalies were detected 48 hours, 30 hours, 8 hours and 37 minutes before the earthquake. The anomalies are very high and their forms are very similar to that of the main shock. Similar anomalies can also be found in strain curves of other shocks greater than Ms7.0, indicating that such anomalies are prevalent before a great earthquake. In this paper, it is shown that medium aftershocks (Ms5.5,6.0) can also cause Earth's free oscillations. Study of free oscillations is of great significance to understand the internal structure of the Earth and focal mechanisms of earthquakes and to recognize slow shocks, thus providing a scientific basis for the prevention and treatment of geological disasters and the prediction of future earthquakes. [source] Satellite Thermal Infrared Earthquake Precursor to the Wenchuan Ms 8.0 Earthquake in Sichuan, China, and its Analysis on Geo-dynamicsACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009Lejun WEI Abstract: Based on an interpretation and study of the satellite remote-sensing images of FY-2C thermal infrared 1st wave band (10.3,11.3 ,m) designed in China, the authors found that there existed obvious and isolated satellite thermal infrared anomalies before the 5.12 Wenchuan Ms8.0 Earthquake. These anomalies had the following characteristics: (1) The precursor appeared rather early: on March 18, 2008, i.e., 55 days before the earthquake, thermal infrared anomalies began to occur; (2) The anomalies experienced quite many and complex evolutionary stages: the satellite thermal infrared anomalies might be divided into five stages, whose manifestations were somewhat different from each other. The existence of so many anomaly stages was probably observed for the first time in numerous cases of satellite thermal infrared research on earthquakes; (3) Each stage lasted quite a long time, with the longest one spanning 13 days; (4) An evident geothermal anomaly gradient was distributed along the Longmen seismic fracture zone, and such a phenomenon might also be discovered for the first time in satellite thermal infrared earthquake research. This discovery is therefore of great guiding and instructive significance in the study of the earthquake occurrence itself and the trend of the post-earthquake phenomena. [source] RS and GIS-based Statistical Analysis of Secondary Geological Disasters after the 2008 Wenchuan EarthquakeACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009Jianping CHEN Abstract: Using RS and GIS means, this article analyzes the general geological characteristics and the structural belt distribution features in Wenchuan County, Sichuan province, P.R. China as well as the characteristics of the large-scale landslides, mud-rock flows, earthquake lakes, etc., after the earthquake on May 12, 2008. Based on the above work, comprehensive indoor and outdoor research is launched on disaster distribution characteristics and their relationship with earthquakes, terrains, strata, lithology, and structures. Weights of evidence method is utilized to quantitatively analyze and evaluate the spatial distribution of secondary geological disasters after the earthquake occurred. 3 remedying grades for secondary geological disasters are derived from the results of the weights of Evidence, followed by suggestions given to remedy earthquake secondary disasters. [source] Risk Assessment and Treatment Countermeasures for the Barrier Lakes of Wenchuan Earthquake on May 12th, 2008ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009Fawang ZHANG Abstract: This paper introduced the first hand investigation results of the risk and treatment measures for the barrier lakes triggered by the earthquake of Wenchuan. Characteristics of 10 barrier lakes were investigated and analyzed; procedure and methods for barrier lake treatment were brought forward. The dams of the barrier lakes can be classified as two classes: block rock in the south and loose deposit in the north. All the barrier dams were stable at the time of investigation, but water drainage channel needed to be constructed and to be protected from blockage or collapse. After the rain season of 2008, some dams needed to be consolidated, and change the barrier lakes to reservoirs. [source] Abnormal Phenomena Recorded by Several Earthquake Precursor Observation Instruments Before the Ms 8.0 Wenchuan, Sichuan EarthquakeACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009Zuxi OUYANG Abstract: The paper introduces the anomalies observed by digital tiltmeter, cross-fault deformation meter, 4-component borehole strainmeter and geothermometer before May 12, 2008, Ms8.0 Wenchuan earthquake, Sichuan. The digital tiltmeter installed in the epicentral region in Shifang County recorded the tilt anomalies 15 days before the earthquake with variation amplitude of 3.7 times larger than the annual deviation of 2007. The cross-fault deformation meter installed at Zimakua station on the Xianshuihe-Anninghe fault zone detected displacement anomaly occurring since 2006 with the variation amplitude exceeding the cumulative value of the last ten years. Five borehole strainmeter stations in the Chongqing section of Three Gorges Reservoir area observed unconventional strain changes occurring in the period from May 1 through 12, 2008. Among them, the strainmeter at Wanzhou station recorded the great compression strain rate on the EW component at 14:00 o'clock of May 10, and the anomaly amplitude was so large that the instrument output exceeded its dynamic range, corresponding to a level of ,104 nanostrains. The geothermometers installed in Xi'an, Chongqing and Xichang recorded the sudden temperature changes from November 2007 to January 2008 with the variation amplitudes several times larger than the ordinary deviation. The above phenomena and the criteria for distinguishing the anomalies from background fluctuations are discussed in this paper. [source] Surface Rupture and Co-seismic Displacement Produced by the Ms 8.0 Wenchuan Earthquake of May 12th, 2008, Sichuan, China: Eastwards Growth of the Qinghai-Tibet PlateauACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2008DONG Shuwen Abstract An earthquake of Ms 8 struck Wenchuan County, western Sichuan, China, on May 12th, 2008 and resulted in long surface ruptures (>300 km). The first-hand observations about the surface ruptures produced by the earthquake in the worst-hit areas of Yingxiu, Beichuan and Qingchuan, ascertained that the causative structure of the earthquake was in the central fault zones of the Longmenshan tectonic belt. Average co-seismic vertical displacements along the individual fault of the Yingxiu-Beichuan rupture zone reach 2.5-4 m and the cumulative vertical displacements across the central and frontal Longmenshan fault belt is about 5,6 m. The surface rupture strength was reduced from north of Beichuan to Qingchuan County and shows 2,3 m dextral strike-slip component. The Wenchuan thrust-faulting earthquake is a manifestation of eastward growth of the Tibetan Plateau under the action of continuous convergence of the Indian and Eurasian continents. [source] Haiti,Moving on after the EarthquakeACADEMIC EMERGENCY MEDICINE, Issue 7 2010Rahul K. Khare MD No abstract is available for this article. [source] | ||||||||||||||||||||||||||||||||||||||||