Table of Content

30 March 2014, Volume 36 Issue 1

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A PRELIMINARY APPROACH TO THE ACTIVITY OF KUMUKOL ANTICLINE

SUN Hao-yue, HE Hong-lin, FU Bi-hong, YANG Shun-hu, Yoshiki SHIRAHAMA, Yasutakyr IKEDA, Kenichi KANO, Tomoo ECHIGO

2014, 36(1):  1-13.  DOI: 10.3969/j.issn.0253-4967.2014.02.001

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Kumukol Basin, located at the north margin of the Tibetan plateau, is separated from the Qaidam Basin by the Qimantag Range geographically. It is the transitional region between the Tibetan plateau and Qaidam Basin, and also the leading edge of the growing main body of the plateau. Nowadays, East Kunlun Fault and Altyn Tagh Fault, two significant strike-slip faults of Tibetan plateau, as well as the compressional Qimantag folding thrust system, delimit the southern, western and northern borders of the basin, respectively. Therefore, the study on the tectonic deformation and tectonic evolution of the basin will play an important role in understanding the style and mechanism of the eastward expanding of Tibetan plateau.
Although Kumukol Basin is delimited by strongly active strike-slip faults, a very large anticline is growing in the basin, with a similar strike of NWW-SEE to the Qimantag folding thrust system and the folds in Qaidam Basin, such as Youshashan fold, suggesting that the basin is compressional. In this study, the lateral growth of this anticline is revealed by the analysis on the topographic profiles and distribution of terraces. A conclusion, as well, is made that the large proluvial fan at the east segment of the anticline is a result of the glacier melt water based on the field survey and dating of terrace samples. According to the OSL and ¹⁰Be exposure ages, the age of the fan is 87.09±2.31ka～102.4±3.7ka, and accordingly, we can get a maximum uplift rate of(2.78±0.28)mm/a～(3.28±0.28)mm/a for the anticline since late Pleistocene. Tectonically, Kumukol Basin is highly similar to Qaidam Basin on its north, both are strongly active and controlled by the regional NEE compression stress field of the Altyn Tagh Fault at its south.

ACTIVE FOLDING AND ACTIVE FLEXURAL-SLIP FAULT SCARPS ON MINGYAOLE ANTICLINE, WEST MARGIN OF TARIM

YANG Xiao-dong, CHEN Jie, LI Tao, LI Wen-qiao, LIU Lang-tao, YANG Hui-li

2014, 36(1):  14-27.  DOI: 10.3969/j.issn.0253-4967.2014.02.002

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In recent times, some moderate-large earthquakes occurred in active folds and thrusts, which seem not directly related with known active faults on the surface and did not form surface ruptures. Although such individual earthquakes might correspond to a known surface active fault, most of them occurred under active folds, formed by displacement of burial thrusts which are located at depth of tens kilometers beneath the folds. Stein named such earthquake as "folding earthquake". It is quite a challenging issue to study and assess the seismic hazards of folding earthquakes occurring in compressive tectonic regions with active folds and burial thrusts. Derived from active folding secondary faults such as flexural-slip faults, bend-moment faults, it is easier to identify that the fold itself. These secondary faults have coseismic slip at the surface and record the active history of seismogenic thrusts which provide an effective way to study the seismic activity of blind thrusts. Many flexural-slip fault scarps are developed on several terrace surfaces at the two limbs of Mingyaole anticline, located along the western margin of the Tarim Basin. These scarps mainly form on the limb of steep beds closest to active axial surfaces(dips of 74°～89°, 18°～20° and 45°～60°, separately), within a range of 50～1 200m from active axial surface, and most are 90～1 000m wide. Overall, the height of the flexural-slip fault scarps gradually deceases away from the active axial surface. These scarps occur at nearly equidistant or multiple distance spacing on the same terrace surface. The strike of the flexural-slip fault scarp is consistent with the strike of underlying bedrock, which is dominated by interbedded medium-thick layered sandstone or fine-grain sandstone with similar rock mechanical properties. Since the abandonment of terrace T3 at the south limb of the Mingyaole anticline, the shortening rate and uplift rate absorbed by flexural-slip faults are at least (1.0±0.2)mm/a, (1.2±0.1)mm/a, respectively. Movement of the flexural-slip faults is characterized by repeatability and neo-activity.

THE RELATIONSHIPS BETWEEN NEOTECTONIC ACTIVITY OF THE MIDDLE SEGMENT OF DARI FAULT AND ITS GEOMORPHOLOGICAL RESPONSE, QINGHAI PROVINCE, CHINA

LIANG Ming-jian, ZHOU Rong-jun, YAN Liang, ZHAO Guo-hua, GUO Hong-mei

2014, 36(1):  28-38.  DOI: 10.3969/j.issn.0253-4967.2014.02.003

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There are numerous Late Quaternary active faults in Dari area, Qinghai Province, with the major strike orientation of NW-NWW and SN. Through analyzing of satellite images and field investigation, we observed significant new activity of the middle segment of Dari Fault during Late Quaternary. The Dari Fault locates in the south of Qinghai Province, and it's a left-lateral strike-slip active fault. Along the studied segment, the surface rupture zones of the M7 (3/4) earthquake are still preserved. The rupture styles of the M7 (3/4) earthquake surface rupture zones are varied and diversified in different segments. This feature is represented by changes of local tectonic stress. The Dari area, as a typical active tectonic zone, is ideal for studying the neotectonics and the geomorphological responses. So in this paper, we also discussed the relationship between the tectonic activities and its geomorphological response in the study area. Analysis on ASTER GDEM V2 digital data enabled us to extract the sub-basins and rivers in this region, and finally determine the hypsometric curves and hypsometric integral(HI values)of the sub-basins. Hypsometry is adopted to analyze the evolution processes of six sub-basins of the Yellow River in the study area. The results show that the geomorphological evolution of the six sub-basins is in the stage of maturity, and the evolution process is highly synchronized, indicating the overall result of regional tectonic uplift or subsidence. Furthermore, the distribution characteristics of the hypsometric integrals(HI value)of the sub-basins reveal that the location of low HI value areas coinsides with the distribution of Quaternary graben basins and valleys, reflecting the results of different local tectonic subsidence and erosion. On the other hand, the high HI areas mainly occur where the strike of the Dari earthquake surface rupture zone changes from NWW to NW and where Early Jurassic and Late Triassic granodiorites are distributed, indicating clearly the variation of local tectonics and difference in lithology.

NUMERICAL SIMULATION ON THE CHANGES OF ELASTIC WAVE VELOCITIES OF ROCKS UNDER RESERVOIR BOTTOM DURING WATER STORAGE AND DRAINAGE

ZHOU Bin, SUN Feng, XUE Shi-feng, JIANG Hai-kun, SHI Shui-ping

2014, 36(1):  39-51.  DOI: 10.3969/j.issn.0253-4967.2014.02.004

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In order to know to what degree can elastic wave velocity be influenced by effective stress changes in rock medium at the bottom of reservoir, and the quantitative relationship between changes of elastic wave velocity, pore pressure and effective stress during the process of reservoir water body load-unloading and water infiltration, pre-works have been done on the geological structures and hydrogeologic conditions in the Zipingpu reservoir, Sichuan Province, and its adjacent areas in detail, and a mathematical model was deduced which could describe rock-mass distortion and stability influenced by liquid seepage in porous rock media during the process of reservoir water body load-unloading and water infiltration. On this basis the paper makes a further study to establish a quantitative mathematical model to describe the relationship between elastic wave velocity and effective stress, and also taking Zipingpu reservoir as an example, calcutates the dynamic changes of pore pressure, additional elastic effective stress, and elastic wave velocity using finite element method. The simulation results show that: the change in incremental value of elastic wave velocity during the process of reservoir water body load-unloading and water infiltration is not obvious, the maximum amplitude is only about ±0.013 km/s, and changes mainly concentrate in local areas above 5km depth under the reservoir bottom. The change in incremental value of elastic wave velocity is associated with changes of additional effective stress, similar to reservoir water-level fluctuation in curve shapes. Incremental value of elastic wave is related to location, depth, and additional effective stress of different observation points. The velocity change of P-wave is greater than S-wave at the same observation point. The time sequence changes of elastic wave velocity obtained by this paper are generally similar to the relative velocity variations of the Zipingpu reservoir region obtained by other scholars using seismic ambient noise method, but the variation range is slightly different.

SUPER-SHEAR RUPTURE PROCESS INVERSION OF THE 2010 YUSHU EARTHQUAKE

ZHANG Li-fen, Iman Fatchurochman, YAO Yun-sheng, LI Jing-gang, LIAO Wu-lin, WANG Qiu-liang

2014, 36(1):  52-61.  DOI: 10.3969/j.issn.0253-4967.2014.02.005

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On 13, April, 2010, a great earthquake of M_W7.0 occurred in Yushu County, Qinghai Province, which is another big one in China since 2008 Wenchuan earthquake. And with seismic wave data, InSAR data and field investigations, many researchers studied the focal mechanism and source rupture process of this earthquake and many valuable results were obtained. However, there are some arguments on the rupture velocity. Some think that this earthquake is a super-shear rupture event, and some insist on opposite opinion. In order to explore whether it is a super-shear rupture event or not, this study chooses the teleseismic wave data recorded by 33 seismic stations with epicentral distances between 30～90 degrees, good azimuth coverage and high signal-noise ratio to reexamine the rupture process using Yagi's program. By comparison of different given rupture velocities in the range of 2.5～5.5km/s, it is found that rupture velocity of 4.7km/s yields the smallest normalized misfit between the observed and synthetic waveforms. And the inversion result is more in accordance with field observation. The relationship between subfault dimension, rise time and rupture velocity is discussed, which shows that the rupture velocity is not so dependent on the two parameters. And by teleseisemic analyses using an envelope deconvolution method with an empirical Green's function, the location and timing of the high-frequency event also show a rupture velocity of 4.7 to 5.8km/s, which is apparently greater than the shear wave velocity in this region. By comprehensive analyses, it can be concluded that the super-shear rupture exists in this earthquake. According to our inversion result, the strike, dip, and rake angle of this earthquake separately is 300, 88 and 4. Beach ball shows the seismogenic fault is of strike-slip type, which is consistent with the Ganzi-Yushu Fault. And the rupture extended to the surface on the northwest and southeast segments of the Yushu Fault with the length of 19km and 31km. Due to the existence of pull-apart Longbao Basin, the central part where the epicenter is did not rupture. By comprehensive analysis, super shear rupture is one of the main reasons that caused serious damage to Yushu County.

EMPIRICAL CRITERIONS AND THEIR PRELIMINARY APPLICATION TO DETERMINE RUPTURE ZONES OF HISTORICAL EARTHQUAKES IN NORTH CHINA FROM SEISMIC INTENSITY DISTRIBUTIONS

LÜ Xiao-jian, WEN Xue-ze

2014, 36(1):  62-79.  DOI: 10.3969/j.issn.0253-4967.2014.02.006

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An earthquake rupture zone is defined as the vertical projection area on the ground surface of the plane(s) on which coseismic slip(s)/rupture(s) occurred along a seismogenic fault zone, and indicates both the position and the extension of a seismic source fault zone/rupture zone. Determination of rupture zones of strong and major earthquakes occurring in the long-past history is an important foundation for identifying seismic gaps, studying and forecasting seismic potentials. Several modern techniques and methods are available to determine rupture zones of modern strong and major earthquakes. However, the relevant methods need to be developed if we hope to determine the rupture zones of the historical events. Taking North China(108°～124°E, 32°～42°N)as a research region, this paper tries to establish the empirical criterion that can be used to determine both positions and extensions of the rupture zones of strong and major earthquakes using data of modern seismic intensities/coseismals and seismotectonics and surficial geologic environments of seismogenic regions, and then makes case studies applying the method developed in this paper. To establish the regional empirical criterion, we systematically collect and analyze the relational material and the research results of the modern earthquakes whose maximum intensities are equal or greater than Ⅶ occurring in North China since 1966, including the surficial geologic-environments, the seismogenic faults and their movement styles, intensity distributions, the inversion of seismic fracture process, the aftershock distributions and the coseismic deformation. Based on those data, we determine the rupture positions and extensions among the seismic intensity spans of eight modern strong and major earthquakes occurring in North China. To compare with the other regional empirical criterions and making up for the inadequacy of the data in North China, we also determine the rupture zones and their extensions among the seismic intensity spans of the 2008 Wenchuan earthquake, Sichuan and the 2010 Yushu earthquake, Qinghai. Our researches show that a close correlation exists among the seismic intensity spans in which the rupture zones extend, with respect to the highest seismic intensities and the surficial geologic-environments of seismogenic regions. Based on the correlations, we establish two empirical criterions that can be used to determine both positions and extensions of rupture zones of historical strong and major earthquakes in two kinds of surficial geologic-environments, regions of basement rocks and regions covered by thick loose sediments of the Quaternary, respectively, in North China, from seismic intensity distributions. In this paper, we also put forward relevant thinking and methods for determining the widths of rupture zones of historical events by combining information from seismotectonics and distributions of modern small earthquakes/aftershocks. As an application test, we use the method presented in this study to determine rupture zones of five historical events, and the results prove that the empirical criterions and the corresponding methods developed in this study are effective to determine rupture zones of historical strong and major earthquakes in North China.

ANALYSIS ON THE SEASONAL VARIATION OF THE AZIMUTH AND STRENGTH OF AMBIENT NOISE ENERGY IN NINGXIA AND ITS ADJACENT REGION

XIE Xiao-feng, YANG Wei, LI Jun, LIN Jian-min, WANG Wei-tao, YAO Lin, LÜ Jun-qiang

2014, 36(1):  80-89.  DOI: 10.3969/j.issn.0253-4967.2014.02.007

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The reconstruction of Green function by cross-correlating long time ambient noise has been extensively used by seismology community and found its applications in many fields such as structural inversion and stress-related velocity monitoring. Analysis on the ambient noise energy, especially its azimuthal distribution and seasonal variation is now becoming more and more important to obtain reliable and precise information from noise cross-correlation function(NCF). In this paper, more than four years vertical records of 33 broadband stations in Ningxia and its adjacent region are cross correlated and stacked monthly to obtain the distribution and variation of noise energy for both 5～10s and 10～20s periods range using normalized background energy flux method. Seasonal variations of strength for both ranges are observed and agree well with the ocean wave activity, which are strong in winter in the northern hemisphere and relatively weak in summer for same hemisphere. But the azimuthal variation are different. For 5～10s noise, the energy mainly comes from the costal line of southeast China. For 10～20s noise the azimuth of the dominant energy has strong seasonal variation. Back projections of the corresponding dominant noise energy azimuth range indicate that the noise field in Ningxia is controlled by several oceans simultaneously but certain ocean may take the main control on the overall noise energy distribution. Due to the none-uniform and none-random properties of noise filed there, we suggest that evaluation of noise field characters should be made before further studies are conducted, especially for time lapse based investigation.

CONSTRUCTION OF BASIC EARTHQUAKE-TRIGGERED LANDSLIDES DATASET FOR SEVERAL LARGE EARTHQUAKE EVENTS AT THE BEGINNING OF THE TWENTY-FIRST CENTURY

XU Chong, XU Xi-wei

2014, 36(1):  90-104.  DOI: 10.3969/j.issn.0253-4967.2014.02.008

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Since the May 12, 2008 Wenchuan M_W7.9 earthquake occurred, the authors have developed new standards for building earthquake-triggered landslide inventory, selecting remote sensing images, and building attribute database based on characteristics of earthquake-triggered landslides and optical remote sensing images. The construction of the basic earthquake-triggered landslides database related to the four earthquake events occurring at the beginning of the twenty-first century is introduced, including, the May 12, 2008 Wenchuan M_W 7.9 earthquake, China, which triggered at least 197,481 landslides, the April 14, 2010 Yushu earthquake, China, that triggered at least 2036 landslides, the January 12, 2010 Haiti M_W 7.0 earthquake, which triggered at least 30,828 landslides, and the Aysén Fjord M_W 6.2 earthquake, Chilean, which triggered at least 1000 landslides. Differences between the database constructed by us and previous results are analyzed. In conclusion, practicable value and scientific significance of these basic earthquake-triggered landslides databases are analyzed, such as, the importance on spatial distribution and hazard analysis of earthquake-triggered landslides, prevention and mitigation for landslide and debris flow disaster in earthquake struck areas, the significance in analyzing magnitudes of earthquake, movement behavior of active fault, seismic intensity information, and essential data for river and landscape evaluation in earthquake stuck areas, and the use in constructing correlation of global earthquakes and landslides triggered by the earthquakes.

STUDY ON THE VOLCANIC EDIFICE AND PETROLOGICAL, MINERALOGICAL CHARACTERISTICS OF ASHI VOLCANO IN WEST KUNLUN MOUNTAINS

SHEN Huan-huan, XU Jian-dong, YU Hong-mei, ZHAO Bo, JI Ling-yun

2014, 36(1):  105-122.  DOI: 10.3969/j.issn.0253-4967.2014.02.009

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Ashikule Basin is located in the‘arc’intersection of NE-trending Altyn Tagh Fault and NW-trending Kangxiwar Fault, in which there are frequent tectonic activities, and more than 10 volcanoes are developed, including Ashi volcano, the latest active volcano in the Ashikule volcanic group. This paper conducts a detailed study on the Ashi volcano from four aspects, including volcanic geology, lava and phenocryst composition, microstructure features and geothermobarometer. The results show that Ashi volcano consists of volcanic cone and lava flow, and specifically the body of the cone is built by early scoria cone and later spatter cone and the lava flow with the area of about 33km² is divided into four flow units. The lavas belong to shoshonite, trachyandesite in composition, and show porphyritic texture under microscope. The main phenocrysts are plagioclase(major in andesine)and pyroxene(including augite, bronzite and hypersthenes); The matrix is glassy, cryptocrystalline, and phaneritic, part of which has lots of feldspar and pyroxene microlites. The phenocryst-liquid equilibrium temperature is 1 104～1 194℃, and the equilibrium pressure is 570～980MPa, indicating that the depth of the magma chamber is about 18.92～32.29km.

STUDY ON THE SOLID PRODUCTS FROM MUD VOLCANO IN NORTH TIANSHAN MOUNTAINS, XINJIANG AND DISCUSSION ON ITS GENETIC MECHANISM

YANG Xiao-fang, YU Hong-mei, ZHAO Bo, XU Jian-dong, GAO Xiao-qi, ZHANG Tao

2014, 36(1):  123-136.  DOI: 10.3969/j.issn.0253-4967.2014.02.010

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The mud volcanoes are located in the piedmont downwarp belt of the North Tianshan Mountains in Xinjiang, and all developed at the axis of the anticlinal fold. In this study, based on the geological background and activity of mud volcanoes, we carried out a detailed field investigation on these mud volcanoes at four sites, including Baiyanggou, Aiqigou, Dushanzi and Huoerguosi, and analyzed the particle size, microscopic morphology and composition of the collected samples. The results show that the eruptive types of these mud volcanoes in this area include mud cone, mud shield, mud basin, mud pool and mud hole. The mud liquid surfaces are calm, and bubbling frequency is low. The largest diameter of the nozzle is 2.5m, and the farthest distance of discharged mud flow is about 6.5 meters. The particle sizes of the samples with the similar average sizes are mostly in the range of 0.3～100μm, the medium sizes focus on 5～10μm, and all of the samples are characterized by poor sorting. The column diagrams are generally unimodal distribution and the samples show quite positive skewness in particle size distribution symmetry. The matrix is composed mainly of clay minerals, containing <15% mineral grains mainly of quartz and feldspar, and there are some iron particles in Baiyanggou and Aiqigou samples. According to the analyses, it is proposed that the mud volcanoes in North Tianshan Mountains have the same material source, which is from the middle-lower Jurassic strata, and the high pressure in the strata can be attributed mainly to tectonic activity in the region. At present, the activity of mud volcanoes is relatively weak, and it is unlikely to cause a serious disaster in the near future.

REMOTE SENSING DETECTION OF VOLCANIC ASH CLOUD USING INDEPENDENT COMPONENT ANALYSIS

LI Cheng-fan, DAI Yang-yang, ZHAO Jun-juan, YIN Jing-yuan, ZHOU Shi-qiang

2014, 36(1):  137-147.  DOI: 10.3969/j.issn.0253-4967.2014.02.011

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The volcanic ash cloud is mainly composed of volcanic ash debris and gases. The adequate mixture of the two can form acidic aerosols. It not only causes the major global climate and environmental changes, but also seriously threatens the aviation safety. Remote sensing can quickly and accurately obtain the information of the surface's and the atmosphere's changes; therefore it is playing an important role in the monitoring of volcanic activity. In recent years, with the advancement of sensor technology, the thermal infrared remote sensing technology has become an important means of detecting the volcanic ash cloud. However, due to the large amount of spectral bands and data, the remote sensing data have pretty strong band correlation and obvious information redundancy problem, all of which have decreased to a certain degree the detecting accuracy of volcanic ash cloud. Therefore, it is necessary to introduce new data processing methods into the volcanic ash cloud remote sensing detection field. Principal component analysis(PCA)can compress a large number of complex information effectively into a few principal components; as a result, it is widely applied in the data compression and hyperspectral remote sensing field. Independent component analysis(ICA)is a recently developed new data processing method which can linearly decompose the observed data into mutually dependent components, and achieve the decorrelation and redundancy elimination of remote sensing data; so it has certain potential in volcanic ash cloud detection. A remote sensing detecting algorithm of volcanic ash cloud, which uses ICA method, is proposed after the exploration of the physics and chemical properties of volcanic ash cloud. This paper takes the MODIS remote sensing image of Iceland's Eyjafjallajokull volcanic ash cloud on April 19, 2010 as data source. It uses ICA in volcanic ash cloud detection on the basis of the principal component analysis(PCA)processing of MODIS image, and gives comparison among these following parties: the detected results, the relevant research results, United States Geological Survey(USGS)standard spectral database and SO₂ concentration distribution. The results show that: ICA can successfully obtain the information of the volcanic ash cloud from MODIS image; the detected volcanic ash cloud has a good consistency with the USGS standard spectral database and the SO₂ concentration distribution, thus, it can obtain pretty good detection results.

CONTEMPORARY TECTONIC DEFORMATION IN NORTH CHINA BY USING THREE-DIMENSIONAL SIMULATION

HU Meng-qian, DENG Zhi-hui, LU Yuan-zhong, SONG Jian, LU Yu, ZHU Xiu-yun, SUN Feng

2014, 36(1):  148-165.  DOI: 10.3969/j.issn.0253-4967.2014.02.012

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Based on ANSYS parallel software platform, and according to active tectonic block region division and distribution of active faults in North China, and combined with GPS data, the range of the numerical model is defined as 99.8°～121.4°E, 27.9°～42.3°N, which contains a majority of the North China active tectonic block region and parts of other block regions including the Tibetan plateau, the Xiyu, South China, and the Northeastern Asia. The model is divided into 416582 elements whose average side length is 25km with 582392 nodes. The main research results are: (1)Simulation of crustal movement velocity and analysis. The results show that the velocity of crustal movement in North China as a whole decreases from east to west and increases from north to south. It is an almost match between simulation results and GPS observed velocity field. (2)Simulation of the slip of faults and analysis. Considering all known late Quaternary active faults in North China in the model and according to the simulation results, the slip of faults obtained from simulation and that from geological survey are almost consistent. (3)Simulation of strain fields and analysis. By numerical simulation, the minimum strain and the maximum principal strain in North China in 1999-2004 and 2004-2007 are calculated. The horizontal strain direction in North China is in accord with the strain direction obtained from inversion of focal mechanism solutions, GPS observations, etc. by previous studies.

APPLICATION OF PS-InSAR TECHINQUE TO MEASUREMENT OF CRUSTAL DEFORMATION ALONG THE NORTH FRINGE FAULT ZONE OF WEST QINLING MOUNTAINS

MENG Xiu-jun, QU Chun-yan, SHAN Xin-jian, MA Chao, XU Xiao-bo

2014, 36(1):  166-176.  DOI: 10.3969/j.issn.0253-4967.2014.02.013

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Differential Synthetic Aperture Radar Interferometry (D-InSAR) is a newly developed technique for monitoring large-scale ground deformation with some prominent advantages such as high accuracy and pantoscopic view. The vertical crustal deformation accuracy can be measured by D-InSAR technology to the millimeter level, but due to restrictions of spatial, temporal decorrelation and atmospheric delay, the application to the monitoring of the crust long-term slow deformation is limited. The Permanent Scatterers approach, which is based on conventional InSAR technique, puts emphasis on processing time series of SAR interferograms by recognizing and analyzing single scatterers with a stable backscatter intensity or reliable phase behavior in time, to study the deformation histories of the earth's surface in a long time series. The PS approach can better conquer problems of temporal and spatial decorrelation, also the atmospheric delay effect, which will improve the efficiency of datum utilization when measuring large time scale deformation events. The PS-InSAR, as an innovation of D-InSAR technology, can overcome the loss of coherence time, and meanwhile, calculate and eliminate the atmospheric effects to ensure the normal operation of the interferometric processing. It acquires the accumulated deformation and its rates at the coherent points in the images.
In this paper, the basic principle, advantage and status of PS-InSAR are introduced. The slight deformation of Gangu area in the fault zone along the north fringe of west Qinling Mountains which is one of the major left-lateral strike-slip active faults in northeastern margin of Tibetan plateau is monitored by PS-InSAR technology using 14 scenes of ENVISAT ASAR data from May 2008 to September 2010. The result shows that the rate of the north wall of the fault zone is -1～-2mm/a, the rate of the south wall of the fault is 3～4mm/a, and relative slip rate between the two walls of the fault zone in Gangu area along the north fringe of west Qinling Mountains is approximately 5mm/a; the points target deformation rate and deformation direction both match with the left-lateral motion feature of the north fringe fault zone of west Qinling Mountains, and results have a good agreement with the study results by other scholars. This suggests that the PS-InSAR technology is capable of detecting crustal small deformation.

RESEARCH ON THE DEFORMATION MONITORING OF CHANGBAISHAN VOLCANO BASED ON PSINSAR TECHNIQUE

TANG Pan-pan, SHAN Xin-jian, WANG Chang-lin

2014, 36(1):  177-185.  DOI: 10.3969/j.issn.0253-4967.2014.02.014

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This paper introduces PSInSAR technique for monitoring the deformation of Changbaishan volcano. Two sorts of images, including 19 in the time interval 1992-1998 acquired by JERS-1 SAR sensor and 14 in 2007-2010 acquired by ASAR, are available. The results demonstrate that: the Tianchi volcano had uplifted in the both periods of time. From 1992 to 1998, the Tianchi volcano was active with a mean deformation rate about 6mm/a in the line of radar sight. By contrast, a lower value as much as 3mm/a indicated that the volcano was more stable between 2007 and 2010. A significant character can be realized that deformation occurring around the crater lake, maybe caused by magma activity, was larger than the areas away from volcano. The leveling data acquired between 2006 and 2009 were used to validate the PSInSAR results, and it shows they agree well with each other. What's more, because of larger cover in space dimension, the PSInSAR technique could help us better understand the deformation characteristic of Tianchi volcano, and make a good complement to the field survey.

TEMPORAL EVOLUTION OF FOCAL DEPTHS OF AFTERSHOCK SEQUENCE FOLLOWING LIJIANG M_S 7.0 EARTHQUAKE AND THE IMPLICATION FOR RHEOLOGICAL PROPERTY OF THE MIDDLE CRUST

SONG Juan, ZHOU Yong-sheng, YANG Wei-hong

2014, 36(1):  186-195.  DOI: 10.3969/j.issn.0253-4967.2014.02.015

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The depth distribution of aftershocks of the 1996 Lijiang M_S7.0 earthquake is strongly time-dependent. Events occurring shortly after the main shock had deeper focal depths, and as the time going on, the focal depth of the aftershocks became shallower and shallower, i.e. the cutoff depth of seismicity became shallower and shallower with time. As we know, the lowermost events occur around the depth of brittle-plastic transition, and this depth depends on strain rate. The postseismic deformation model inferred from GPS data show that the major contribution of postseismic strain release comes from the lower layer of the crust. These results suggest that significant afterslip is related to viscous relaxation of lower layer. We estimated the lower bound of the strain rate according to Marone's et al.(1991)afterslip model and the slip data observed at the surface of Xianshuihe Fault. The results show that the strain rate is high after the main shock, and decreases gradually with time. We calculated the strength profile of middle crust based on flow law of wet quartz, estimated strain rate, temperature profile determined using the heat flow data at Lijiang, as well as crustal structure based on P wave velocity. By comparing the cutoff depth of seismicity and the brittle-plastic transition depth of the middle crust, we found the two depths are consistent to each other. We suggest the temporary existence of deeper small events after main shock and the depth distribution of aftershock is due to the changing brittle-plastic transition of the middle crust corresponding to strain rate variation from high to lower values after the main shock, and this kind of change is the manifestation of rheology of the middle crust.

STUDY ON CITY’S EARTHQUAKE EMERGENCY DISPOSAL SCHEME-RELATED TECHNOLOGY

XU Jing-hai, NIE Gao-zhong

2014, 36(1):  196-205.  DOI: 10.3969/j.issn.0253-4967.2014.02.016

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Earthquake is one of most serious natural disasters in China. In order to effectively mitigate earthquake disaster, three catalogues of jobs have been done under the leadership of China Earthquake Administration. Earthquake emergency is one of such important jobs, which could save life and reduce disaster damage. Earthquake emergency preplan plays a key role in this work, and provides foundation for disaster rescue. Although the emergency preplans get great achievements in many earthquake disaster reliefs, they also show some drawbacks in the practical applications.
In this paper, we analyze the characteristics of Chinese earthquake emergency preplans and find that the framework of emergency preplans is clear, but the provisions on emergency operations are macroscopical and not easy to use; the structures of the emergency preplans are generically similar in the whole country and lack of pertinence to specific disaster areas or professional industries; the connections between earthquake disaster emergency preplans and other disaster emergency preplans are weak; the dynamic managements of the preplans need to be enhanced.
In order to complement the emergency preplans, earthquake emergency response disposal scheme is discussed in this paper, which is an emergency disposal work plan for detailed emergency events after an earthquake from technical perspective and aims at directing earthquake emergency response. The relationships between the emergency preplans and the disposal schemes are introduced. The core difference between them is in that a preplan focuses mainly on who should respond to the emergency event, while a disposal scheme is more concerned about how to cope with the emergency event.
We also present the components of the disposal schemes, which include disposal scheme framework, emergency decision-making knowledge and supported information platforms. Then the work principle of the disposal schemes is described based on these components. In this principle, earthquake emergency decision-making knowledge is used to amend the disposal scheme framework to generate the emergency disposal scheme with the support of information technologies. Within the disposal schemes, three kinds of the disposal countermeasures, namely, descriptive emergency countermeasures, the countermeasures from earthquake emergency professional models and the countermeasures from GIS and RS technical platforms are introduced.
Taking urban level as an example, the urban disposal scheme framework is depicted. It is composed of five parts: geographic environment in disaster area, earthquake information, estimated disaster information, emergency countermeasures and other related countermeasures. Then the components of the decision-making knowledge are introduced. The knowledge representations result from comprehensive processing of various information related to earthquake emergency response and rescue.
This paper lays the foundation for the earthquake emergency response disposal scheme generation and application, which helps to solve the problems of the earthquake emergency preplans. In future, the detailed implementation and application methods of earthquake emergency decision-making knowledge will be studied and used to realize the computer-aided generation of the disposal schemes.

ANALYSIS OF THE PUBLIC AWARENESS OF EARTHQUAKE PREVENTION AND DISASTER REDUCTION IN WEAK SHOCK AREA：A CASE STUDY IN PINGXIANG, JIANGXI PROVINCE

ZHANG Wen-jia, WEI Ben-yong, SU Gui-wu

2014, 36(1):  206-221.  DOI: 10.3969/j.issn.0253-4967.2014.02.017

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Jiangxi Province is a typical representative of weak shock area in China. By taking Pingxiang as an example, the present situation and characteristics of the awareness of earthquake prevention and disaster reduction of the social public in the weak shock area were analyzed through questionnaire survey. And the effects of publicity and education about seismic disaster reduction were discussed. The main conclusions are as follows: (1)The public's cognition in Pingxiang to the local disasters is in accordance with the frequency of disasters, not match with the impact of individual disasters. The degree of public attention to infrequent disasters like earthquake is low, compared with other disasters, e.g. floods and droughts.(2)Most people in Pingxiang could not fully understand the basic concepts of earthquake and the relationship between seismic phenomenon and earthquake disaster. Local people show little distinguishable ability when faced with earthquake rumors. And their capacity to master the skills about earthquake prevention and disaster reduction is not adequate. The surveyed data show that the mastering level of the public in Pingxiang in escaping skills is better than their emergency medical capabilities.(3)News media and school education are the main ways for the public to acquire earthquake knowledge and skills about earthquake prevention and disaster reduction. Government dissemination activities and science books are also important approaches for public acquisition of earthquake knowledge and earthquake-prevention skills. Few people gained earthquake knowledge and earthquake disaster reduction skills through personal experience. Compared with other regions, the role of Pingxiang Government in the publicity and education of earthquake knowledge and disaster-reduction skills remain to be reinforced.(4)The majority of local people have strong desire to learn more knowledge and acquaint more skills about earthquake prevention and disaster reduction. To raise the public's disaster awareness and improve the coping skills for earthquake prevention and disaster reduction, it is of practical significance to conduct pertinent dissemination and education, and launch earthquake emergency drills.

A COMPARATIVE ANALYSIS BETWEEN INSTRUMENTAL INTENSITY AND SURVEY SPOT INTENSITY OF LUSHAN M7.0 EARTHQUAKE

FENG Wei, JIANG Li-xin, YANG Tian-qing, LI Yang, ZHENG Tong-yan

2014, 36(1):  222-229.  DOI: 10.3969/j.issn.0253-4967.2014.02.018

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Lushan M7.0 earthquake on April 20, 2013 occurred on the southern segment of Longmen Shan Fault zone. It is another strong earthquake after the Wenchuan M8.0 earthquake, rather than an aftershock. A total of 196 people died in Lushan M7.0 earthquake, 21 people missing, and 13019 injured. In this paper, we use the April 20, 2013 Lushan M7.0 earthquake strong motion records to calculate equivalent peak acceleration A_0.5 and convert it into the instrumental intensity. Then, we carry out the comparative analysis of instrumental intensity and surveyed intensity at the spots in the range of 5 kilometers around the stations. The results show a coincidence degree of 58.6% between the instrumental intensity and surveyed intensity, with the deviation less than ±1 degree. Meanwhile, we also recognize that there is a big dispersion of the observed ground motion parameters, even in the same macro-intensity. It is uncertain about the corresponding relationship between the individual station measured ground motion parameter values and the seismic intensity. The damage may be caused by earthquake ground motion characteristics, building types and site conditions and other factors, and therefore the difference between instrument intensity and actual seismic intensity cannot be ignored. On the whole, instrumental seismic intensity has potential for determining the range of seismic intensity, thus to provide quantitative reference, especially, in the absence of earthquake site investigation initially.

OBSERVATIONS ON ULTRAHIGH FREQUENCY EARTHQUAKE SIGNAL

ZHANG Shi-di, LIU Li-qiang, LIU Pei-xun, CHEN Guo-qiang

2014, 36(1):  230-242.  DOI: 10.3969/j.issn.0253-4967.2014.02.019

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Earthquake is a form of tectonic activity, an earthquake contains a lot of information, its frequency range is very wide. So far, the main frequency range of seismic records is below 100Hz, and the ultrahigh frequency seismic information got less attention by researchers. However, high frequency microseismicity can provide important information on micro-activities of fault. This paper introduces a new 100kHz ultrahigh frequency seismometer and its first application on high frequency microseismicity observation. The telemeter has been applied in Dali, Yunnan. Several high frequency microearthquakes were recorded and the corresponding earthquake location and spectral analysis were done. The results show that high frequency microearthquakes caused by crustal movement do exist and can be recorded by our telemeter. The recorded microearthquakes are of magnitudes between M_W=-3.0 and M_W=-1.0, maximum hypocentral distance up to 4.87km, dominant frequency ranging from 100Hz to 300Hz, and maximum frequency as high as 800Hz. It is possible that the ultrahigh frequency microseismicity observation(UFMO) will become a new approach to the study on the tectonic movement.

EXPERIMENTAL RESEARCH ON REGIONAL LOADING PROCESS AND LOCAL DEFORMATION EVOLUTION OF THE SEISMOGENIC FAULT

GUO Ling-li, LIU Li-qiang

2014, 36(1):  243-252.  DOI: 10.3969/j.issn.0253-4967.2014.02.020

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In the present paper, double shear stick-slip model experiments were conducted for simulating the regional loading process of spontaneous earthquake and induced earthquake, and a strain observation system was employed to acquire dada continuously to monitor the local strain changes near fault under the loading process. Regional stress path and local strain path during the whole earthquake process have been described on the stress space and strain space. Though the morphology of local strain path is different greatly from the macroscopical stress path, there is a certain mapping relation on the corresponding transformation stages between stress path and strain path. The evolution trend of local strain path indicates the possible stage of the fault deformation. The strain path of spontaneous earthquake can be divided into three parts: Strain accumulation, linear deviation of shear strain and unstable slip. The strain path of induced earthquake includes four stages: Strain accumulation with positive slope, steady state slip with negative slope, metastable strain stalemate and unstable slip under a disturbance. Spontaneous earthquake and induced earthquake have their own inherent and steady path model, so the fault stability and the possible earthquake type could be judged according to the special strain path.

LONG TIME SERIES ANALYSIS OF IONOSPHERIC TEC DISTURBANCE OVER SEISMICALLY ACTIVE REGION IN SOUTHWEST CHINA DURING LOW SOLAR ACTIVITY

YAN Xiang-xiang, SHAN Xin-jian, CAO Jin-bin, TANG Ji, LIU Zhan, WANG Zhen-jie

2014, 36(1):  253-265.  DOI: 10.3969/j.issn.0253-4967.2014.02.021

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Using data of Crustal Movement Observation Network of China(CMONC)we analyzed variations of total electron content(TEC)over southwest China during a period of low solar and geomagnetic activity in April-October 2008. During that time, six large earthquakes with magnitude M≥6.0 occurred around the southwest region of China. To determine the abnormal TEC signals, a quartile-based process is performed. At each time point we calculated the median M using the TEC values at the same local time for the preceding 15 days. In addition, we calculated the maps of differential TEC from global ionosphere maps(GIM)in the above period. Known that the decisive role in the ionosphere state is performed by space weather effects, we compared the TEC variations with time series of EUV solar radiation, Bz component of the interplanetary magnetic field (IMF), index of geomagnetic activity D_st and planetary index K_p, respectively. It is found that the observed anomalies in the regional TEC are in good correlation with the variations of above solar and geomagnetic activities. We have not detected obvious TEC disturbance before five earthquakes expect for Wenchuan earthquake. In order to additionally check the spatial occurrence of the observed anomalies, we chose a "check-region" with the same geomagnetic latitudes as the epicentral area of the six considered earthquakes, and analyzed the TEC changes. The result shows that the time series of anomalous TEC in "check-region" is similar to the epicentral area, which is dominated by space weather. Therefore, it indicates the difficulties in identifying earthquake precursors in the ionosphere TEC. The seismo-ionospheric coupling process is complex, and it is necessary to strengthen the observation of multi-parameters on the ground, in the atmosphere and ionosphere synchronously.

DISCUSSION ON WHETHER THERE ARE COSEISMIC SURFACE RUPTURES OF THE LUSHAN M_S 7.0 EARTHQUAKE AT LONGMEN AREA AND ITS IMPLICATIONS

LEI Sheng-xue, RAN Yong-kang, WANG Hu, CHEN Li-chun, LI Xi, WU Fu-yao, HAN Fei, LIU Cheng-long

2014, 36(1):  266-274.  DOI: 10.3969/j.issn.0253-4967.2014.02.022

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An M_S 7.0 earthquake attacked southern segment of the Longmenshan Fault zone on 20 April 2013, in Lushan County, Sichuan Province, southwest of China. The seismic intensity of the meizoseismal area of the Lushan event is Ⅰ Ⅹ(the Chinese Seismic Intensity Scale). The meizoseismal area strikes NE, and is approximately 24km long and 11km wide. In the post-earthquake emergency scientific survey, some members found a series of co-seismic surface rupture signs at Longmen Township, one of the most damaged areas by this quake, north of Lushan County. The reported typical surface rupture signs include intensive shear-fissures along the channel at Zhanghuo Group, rotation of bricks near a white tower at Wanghuo Group, and lots of extensive cracks. On the basis of analyzing such surface rupture signs, Han et al., (2013)deduced that there might be a blind fault along Lushan County and Longmen Township(named the Lushan-Longmen presumed blind fault), and this fault probably was the seismogenic fault. Therefore, to confirm whether there is a potential seismogenic fault along Lushan and Longmen is very important not only to research of seismogenic fault for this earthquake but also to the reconstruction in the disaster-hit areas. Through surface ruptures surveying and trench excavating, we conclude that: there are no co-seismic surface ruptures at Longmen. Meanwhile, artificial seismic prospecting outcome, which shows nonexistence of the Lushan-Longmen presumed blind fault at least 800m below the ground surface, also supports our idea. Consequently, the reported shear-fissures and extensive cracks are not produced by the seismogenic fault, but most likely by ground shaking during the earthquake.

OVERVIEW OF VISUALIZATION METHODS OF THREE DIMENSIONAL TOPOGRAPHIC DATA

ZHANG Ling, YANG Xiao-ping, WEI Zhan-yu, HANG Wei-liang

2014, 36(1):  275-284.  DOI: 10.3969/j.issn.0253-4967.2014.02.023

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With rapid improvement in resolution of three dimensional topographic data, more and more high-resolution remote sensing data are applied in the study of geomorphology and seismo-geology. The contour map, hill shading map and hypsometric tint map are original visualization methods of plan view for three dimensional topographic data. They all have their own advantages and have been widely used in screen display and plane graphics, and they usually are mixed and merged to enhance the expression ability of information as a complement to each other. But the results still can not completely satisfy the demand of displaying and exploring the hiding information. As a result, how to utilize sufficiently the high-resolution remote sensing data and various visualization methods to make better expression of topography and detect small geomorphic features has been concerned by many scientists.
A new topographic parameter, termed openness, and a new visualization method, termed RRIM, have been developed to enhance the three-dimension effect and produce a fine image of topographic structure with no shade, which does not need any professional ability for its audiences and additional instruments. In the meanwhile, the RRIM has the incomparable predominance in identifying the subtle tectonic geomorphic features, which is very important in the research of geomorphology. If the three dimensional topographic data have the highest resolution and positioning accuracy relative to the hand-held measuring devices in field work, the geomorphologic interpretation work indoors will take place of the field work in a large extent. As a result, the new visualization not only can improve work efficiency, but also reduce the amount of field work. For forest area, tough natural conditions area and no access area which are of research value, RRIM provides a better method and has an important practical value.
Finally, we hope that the new visualization method can play a larger role in geomorphologic interpretation work, especially in active tectonics research and active fault mapping.