对古浪8级大震孕育和发生的构造环境及发震模型的讨论

通过近年来对古浪8级大震的震源机制解、震区活动构造、地震活动性及深部地球物理资料的研究,进一步探讨了古浪大震孕育和发生的深、浅部地质构造环境和地震地质模型。研究结果认为:古浪地震是在北东-南西向挤压应力作用下。

芦山Ms7.0地震前龙门山断裂带西南段区域形变特征分析及发震模型探讨

利用2010年和2013年两期精密水准测量数据分析了芦山Ms7.0地震前龙门山断裂带西南段的区域形变特征。结果显示,芦山地震前龙门山断裂带西南段的天全-泸定区域垂直形变速率为6~8mm/a,远大于汶川地震前的形变速率,汶川地震对芦山地震前该区域库伦应力值的积累起加速作用;临近四川盆地的雅安至名山区域的垂直形变速率为-3^-6mm/a。从芦山地震和汶川地震的地震破裂带及余震分布区域来看,两次地震中间出现一段"地震空区",应力可能会在空区加速积累,应加强该区域地震监测和预报。

1966年邢台地震群的发震构造模型——新生断层形成?先存活断层摩擦粘滑?

通过对邢台地震极震区浅层探测、新生代深浅构造运动的分期、地壳上地幔结构特征剖析及其与震源参数的对比等研究 ,指出邢台地震区控制早第三纪盆岭构造发育的铲形断裂及其下部向东缓倾的滑脱面与邢台地震的发生无关 ;邢台地震群是在最新构造应力场作用下 ,受北西向断层或横向障碍体阻隔的不连续“深断裂”依次向上撕裂状破裂扩展、引起相邻斜列状深断裂间应力迁移和加载等三维破裂过程的产物 ;邢台地震断层是先存地壳“深断裂”向上撕裂状扩展的“新生断层”。

汶川M_S8.0地震地表破裂带及其发震构造

震后应急野外考察表明,2008年5月12日汶川MS8.0地震在青藏高原东缘龙门山推覆构造带上同时使北川-映秀断裂和灌县-江油断裂两条倾向NW的叠瓦状逆断层发生地表破裂。其中,沿北川-映秀断裂展布的地表破裂带长约240km,以兼有右旋走滑分量的逆断层型破裂为主,最大垂直位移6.2m,最大右旋走滑位移4.9m;沿灌县-江油断裂连续展布的地表破裂带长约72km,最长可达90km,为典型的纯逆断层型地表破裂,最大垂直位移3.5m;另外,在上述两条地表破裂带西部还发育着1条NW向带有逆冲垂直分量、左旋走滑性质的小鱼洞地表破裂带,长约6km。这一地表破裂样式是近期发生的特大地震中结构最复杂的一次逆断层型地表破裂,地表破裂的长度也最长。利用已有的石油地震剖面,结合余震分布和地表破裂带特征等资料构建的三维发震构造模型表明,龙门山推覆构造带现今和第四纪时期以地壳缩短为主,斜滑逆冲型地震表明青藏高原中东部的水平运动在华南地块与巴颜喀拉地块之间的龙门山推覆构造带上转化为地壳的缩短和隆升。

青藏高原西北部区域地壳形变、构造地貌与孕震构造模型研究——以2008年与2014年新疆于田7.3级地震为例

为了清晰认识发生于青藏高原西北部2008年与2014年的两次于田MS7.3地震发震构造环境与构造地貌特征,本文利用DEM（数字高程模型）数据分析＂喀喇昆仑—西昆仑—康西瓦地区＂的地形地貌特征,结合区域活动断裂研究资料、相对于塔里木盆地的两期GPS速度场资料和区域运动学特征等讨论两次MS7.3地震所处的青藏高原西北部区域构造环境和地壳运动学特征,分析喀喇昆仑断裂、阿尔金断裂康西瓦段、龙木错-邦达错断裂及贡嘎错断裂所围限的西昆仑地块的地质构造背景、阿尔金断裂西南端发震断裂活动性及孕震环境等发震构造基本条件;进而利用＂地形剖面＂方法及断裂分布特征分析震源区的地形地貌特征,给出晚第四纪以来的地貌形态与发震构造的关系,从区域构造地貌学和GPS地壳运动学的角度探讨中上地壳变形特征及孕震过程;最后讨论区域孕震构造、克尔牙张性裂谷演化过程和地球动力学背景等。通过地形剖面及区域地貌综合分析新疆于田2008年MS7.3拉张型发震构造和2014年MS7.3走滑拉张型地震的发震构造特点的区别,认为2014年发生的地震可能与2008年MS7.3地震同震库伦应力变化、触发过程及震后变形过程密切相关,并且青藏高原西北部地区存在明显的东西向拉张性构造单元,可能与青藏高原1015 Ma以来的地壳减薄过程有关。

基于GPS、水准和强震动观测资料联合反演2013年芦山7.0级地震同震滑动分布

为了更好理解2013年四川芦山MS7.0级地震的发生过程及其与发震构造和地表多种观测资料的动力学关联,本文综合重新定位的余震分布与地质、地球物理信息构建3D发震构造模型,采用水平层状介质模型,并以震区GPS、水准、强震动等同震位移/形变观测资料为约束,联合反演了芦山主震的同震滑动分布.其中,断层解译结果表明震源区包含5条相关断层F1—F5,通过对所有可能的断层组合模型进行反演分析,显示采用F1＋F3＋F4＋F5的组合模型反演效果相对最好,是最可能的发震断层模型.反演得到的芦山主震矩震级为MW6.5,其中同震滑动主要分布在NW倾的主断层F1的断坡周围,最大值为0.86m,滑动角92.88°,纯逆冲型;F1上方反倾的次级断层F3上最大滑动量为0.37m,滑动角119.92°,表现出以逆冲为主兼右滑的斜向反冲作用;而沿另一条反倾的次级断层F4的最大滑动量为0.40m,滑动角97.98°,几乎为纯逆冲作用.此外,震区还存在一个NW缓倾深度为5-8km的浅部滑脱面F5,它分隔了浅部沉积盖层与深部变质基底,限制了其下方F1、F3及F4等断层的同震破裂继续向更浅部扩展.主震时深部F1和F3断层夹持的冲起构造发生了上冲运动,除了使浅层和地表产生响应运动及变形外,还引起冲起构造顶面即F5底面的NE段和SW段分别产生了NE和SWW向调节滑动,最大值0.25m.总之,基于文中构建的F1＋F3＋F4＋F5的发震断层模型,反演结果能很好拟合地表多种观测资料,还能解释地表GPS观测的同震＂左旋＂运动与地震学观测的震源断层逆冲运动的＂不协调性＂.

Dynamic failure mode and energy-based identification method for a counter-bedding rock slope with weak intercalated layers

The dynamic failure mode and energybased identification method for a counter-bedding rock slope with weak intercalated layers are discussed in this paper using large scale shaking table test and the Hilbert-Huang Transform(HHT) marginal spectrum.The results show that variations in the peak values of marginal spectra can clearly indicate the process of dynamic damage development inside the model slope.The identification results of marginal spectra closely coincide with the monitoring results of slope face displacement in the test.When subjected to the earthquake excitation with 0.1 g and 0.2 g amplitudes,no seismic damage is observed in the model slope,while the peak values of marginal spectra increase linearly with increasing slope height.In the case of 0.3 g seismic excitation,dynamic damage occurs near the slope crest and some rock blocks fall off the slope crest.When the seismic excitation reaches 0.4 g,the dynamic damage inside the model slope extends to the part with relative height of 0.295-0.6,and minor horizontal cracks occur in the middle part of the model slope.When the seismic excitation reaches 0.6 g,the damage further extends to the slope toe,and the damage inside the model slope extends to the part with relative height below 0.295,and the upper part(near the relative height of 0.8) slides outwards.Longitudinal fissures appear in the slope face,which connect with horizontal cracks,the weak intercalated layers at middle slope height are extruded out and the slope crest breaks up.The marginal spectrum identification results demonstrate that the dynamic damage near the slope face is minor as compared with that inside the model slope.The dynamic failure mode of counter-bedding rock slope with weak intercalated layers is extrusion and sliding at the middle rock strata.The research results of this paper are meaningful for the further understanding of the dynamic failure mode of counter-bedding rock slope with weak intercalated layers.

Rapid Susceptibility Mapping of Co-seismic Landslides Triggered by the 2013 Lushan Earthquake Using the Regression Model Developed for the 2008 Wenchuan Earthquake

The primary objective of landslide susceptibility mapping is the prediction of potential landslides in landslide-prone areas. The predictive power of a landslide susceptibility mapping model could be tested in an adjacent area of similar geo- environmental conditions to find out the reliability. Both the 2oo8 Wenchuan Earthquake and the 2o13 Lushan Earthquake occurred in the Longmen Mountain seismic zone, with similar topographical and geological conditions. The two earthquakes are both featured by thrust fault and similar seismic mechanism This paper adopted the susceptibility mapping model of co-seismic landslides triggered by Wenchuan earthquake to predict the spatial distribution of landslides induced by Lushan earthquake. Six influencing parameters were taken into consideration： distance from the seismic fault, slope gradient, lithology, distance from drainage, elevation and Peak Ground Acceleration （PGA）. The preliminary results suggested that the zones with high susceptibility of co- seismic landslides were mainly distributed in the mountainous areas of Lushan, Baoxing and Tianquan counties. The co-seismic landslide susceptibility map was completed in two days after the quake and sent to the field investigators to provide guidance for rescue and relief work. The predictive power of the susceptibility map was validated by ROC curve analysis method using 2o37 co-seismic landslides in the epicenter area. The AUC value of o.71o indicated that the susceptibility model derived from Wenchuan Earthquake landslides showed good accuracy inpredicting the landslides triggered by Lushan earthquake.

Detailed reservoir inversion addressing geological problems in reservoir development

In the Ken 71 development block, fluvial facies of the Neogene Guantao Formation and delta facies of the Paleogene Dongying Formation are the main pay beds. It is a multiple oil and water system which is complicated by faults. Characteristics of the block include a dense well network, thin reservoirs, complicated horizontal relationships, and small velocity difference between reservoir and non-reservoir. Therefore, it is difficult to conduct detailed reservoir description for subsequent development project adjustment. We demonstrate a stochastic seismic inversion which aims at detailed reservoir description. It is a technology which utilizes multiple wells, seismic data, and geological calibration and integrates with 3D structural interpretation results to build a 3D multi-fault detailed and constrained geological model. On this basis, we adopted stochastic seismic inversion to conduct a multi-stratum parameters inversion such as impedance and lithology. As a result, thin interbedded strata in the block were well resolved and the results demonstrated the importance of detailed reservoir inversion for oilfield development.

Empirical-Statistical Models Based on Remote Sensing for Estimating the Volume of Landslides Induced by the Wenchuan Earthquake

The Wenchuan Ms 8.0 earthquake on May 12, 2008 induced a huge number of landslides. The distribution and volume of the landslides are very important for assessing risks and understanding the landslide - debris flow - barrier lake - bursts flood disaster chain. The number and the area of landslides in a wide region can be easily obtained by remote sensing technique, while the volume is relatively difficult to obtain because it requires some detailed geometric information of slope failure surface and sub-surface. Different empirical models for estimating landslide volume were discussed based on the data of 107 landslides in the earthquake-stricken area. The volume data of these landslides were collected by field survey. Their areas were obtained by interpreting remote sensing images while their apparent friction coefficients and height were extracted from the images unifying DEM (digital elevation model). By analyzing the relationships between the volume and the area, apparent friction coefficients, and the height, two models were established, one for the adaptation of a magnitude scale landslide events in a wide range of region, another for the adaptation in a small scope. The correlation coefficients (R2) are 0.7977 and 0.8913, respectively. The results estimated by the two models agree well with the measurement data.

MBDA R&T EFFORT ON PULSED AND CONTINUOUS DETONATION WAVE ENGINES

The continuous detonation wave engine（CDWE）can be considered to reduce the environmental conditions generated by pulsed detonation engine（PDE）while reducing the importance of initiation issue and simplifying some integration aspects.Specific experimental programs are performed by MBDA and Lavrentiev Institute to study CDWE operating mode and to address some key points for the feasibility of an operational rotating wave engine for space launcher.It is found that such engine can deliver impressive thrust in a very small package（275 daN for internal diameter of 50 mm and length of 100 mm,kerosene-oxygen engine）and that can be increased with the use of a diverging nozzle.Due to the geometry of the combustion chamber,a plug or aerospike nozzle seems to be the best design,the thrust vectoring capability of this engine（with the local change of the mass flow rate）being a way to solve the problem of attitude control.The heat fluxes are very high but located mostly near the injection wall.This point will help the gasification of the liquid component injected inside the combustion chamber.Some preliminary tests are performed to evaluate the capability of C/SiC composite materials to sustain the very severe mechanical environment generated by the rotating detonation waves.Beyond these first steps,a large scale ground demonstrator allowing to address all issues for a continuous detonation rocket engine using LH2/LOx mixture is designed by MBDA.As the first step toward the development of this large scale engine,a small scale demo is tested in Spring 2010.

Deformation Model Inferred from Focal Mechanisms in the Chinese Mainland and Its Adjacent Areas

We collect seismic moment tensors of the earthquakes occurring from 1900 to 2013 in and around the Chinese mainland and summarize the surface ruptures and displacements of 70 earthquakes with M S≥7. 0. We divide these large earthquakes into three types. Type A contains earthquakes with surface ruptures and displacements. Type B is earthquakes without displacements and Type C is those without any of this data. We simulate a triangular distribution of displacements for Type B and C. Then,we segment these large earthquakes by using their displacements and surface ruptures. Finally,kinematic models are determined from earthquake data and Bicubic Bessel spline functions. The results show that,first of all,the reasonability and spatial consistency of defined models are advanced.Strain rates have better continuity and are comparable with geologic and geodetic results in Himalaya thrust fault zones. The strain rates decrease in the Tarim basin and the Altun Tagh fault zones because of their low seismicity. The direction of compressional deformation in Gobi-Altay is changed from SE to NE and its extensional direction is changed from NE to NW. The extensional deformation in the Ordos block is diminished obviously. Secondly,earthquakes account for 30- 50% of expected motion of India relative to Eurasia determined from the NUVEL-1A model,with a missing component of 20 mm / a which may contain aseismic deformation such as fault creep and folds,the missing parts of earthquake data and elastic strain energy released by potential earthquakes.

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.

Knock prediction for dual fuel engines by using a simplified combustion model

The present work used a methane-air mixture chemical kinetics scheme consisting of 119 elementary reaction steps and 41 chemical species to develop a simplified combustion model for prediction of the knock in dual fuel engines. Calculated values by the model for natural gas operation showed good agreement with corresponding experimental values over a broad range of operating conditions.

Coseismic slip distribution of 2009 L'Aquila earthquake derived from InSAR and GPS data

To better understand the mechanism of the Mw6.3 L＇Aquila （Central Italy） earthquake occurred in 2009, global positioning system （GPS） and interferometric synthetic aperture radar （InSAR） data were used to derive the coseismic slip distribution of the earthquake fault. Firstly, based on the homogeneous elastic half-space model, the fault geometric parameters were solved by the genetic algorithm. The best fitting model shows that the fault is a 13.7 km×14.1 km rectangular fault, in 139.3° strike direction and 50.2° southwest-dipping. Secondly, fixing the optimal fault geometric parameters, the fault plane was extended and discretized into 16× 16 patches, each with a size of 1 kmx 1 krn, and the non-uniform slip distribution of the fault was inverted by the steepest descent method with an appropriate smoothing ratio based on the layered crustal structure model. The preferred solution shows that the fault is mainly a normal fault with slight right-lateral strike slip, the maximum slip of 1.01 m is located in the depth of 8.28 km, the average rake is -100.9°, and the total geodetic moment is about 3.34× 1018 N.m （Mw 6.28）. The results are much closer than previous studies in comparison with the seismological estimation. These demonstrate that the coseismic fault slip distribution of the L＇Aauila earthauake inverted by the crustal model considering layered characters is reliable.

Finite element investigation of the poroelastic effect on the Xinfengjiang Reservoir-triggered earthquake

Coulomb failure stress changes (ΔCFS) are used in the study of reservoir-induced seismicity (RIS) generation.The threshold value of ΔCFS that can trigger earthquakes is an important issue that deserves thorough research.The M s 6.1 earthquake in the Xinfengjiang Reservoir in 1962 is well acknowledged as the largest reservoir-induced earthquake in China.Therefore, it is a logical site for quantitative calculation of ΔCFS induced by the filling of the reservoir and for investigating the magnitude of CFS that can trigger reservoir seismic activities.To better understand the RIS mechanism, a three-dimensional poroelastic finite element model of the Xinfengjiang Reservoir is proposed here, taking into consideration of the precise topography and dynamic water level.We calculate the instant changes of stress and pore pressure induced by water load, and the time variation of effective stresses due to pore water diffusion.The CFS on the seismogenesis faults and the accumulation of strain energy in the reservoir region are also calculated.Primary results suggest that the reservoir impoundment increases both pore pressure and CFS on the fault at the focal depth.The diffusion of pore pressure was likely the main factor that triggered the main earthquake, whereas the elastic stress owing to water load was relatively small.The magnitude of CFS on seismogenesis fault can reach approximately 10 kPa, and the ΔCFS values at the hypocenter can be about 0.7-3.0 kPa, depending on the fault diffusion coefficient.The calculated maximum vertical subsidence caused by the water load in the Xinfengjiang Reservoir is 17.5 mm, which is in good agreement with the observed value of 15 mm.The accumulated strain energy owing to water load was only about 7.3×10 11 J, even less than 1% of the seismic wave energy released by the earthquake.The reservoir impoundment was the only factor that triggered the earthquake.