Table of Content

20 August 2018, Volume 40 Issue 4

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DISTRIBUTION CHARACTERISTICS OF THE AD 1556 HUAXIAN EARTHQUAKE TRIGGERED DISASTERS AND ITS IMPLICATIONS

XU Yue-ren, ZHANG Wei-heng, LI Wen-qiao, HE Hong-lin, TIAN Qin-jian

2018, 40(4):  721-737.  DOI: 10.3969/j.issn.0253-4967.2018.04.001

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A complete understanding to the disasters triggered by giant earthquakes is not only crucial to effectively evaluating the reliability of existing earthquake magnitude, but also supporting the seismic hazard assessment. The great historical earthquake with estimated magnitude of M8.5 in Huaxian County on the 23^rd January 1556, which caused a death toll of more than 830 000, is the most serious earthquake on the global record. But for a long time, the knowledge about the hazards of this earthquake has been limited to areas along the causative Huashan piedmont fault(HSPF) and within the Weihe Basin. In this paper, we made a study on earthquake triggered landslides of the 1556 event along but not limited to the HSPF.
Using the high-resolution satellite imagery of Google Earth for earthquake-triggered landslide interpretation, we obtained two dense loess landslides areas generated by the 1556 earthquake, which are located at the east end and west end of the HSPF. The number of the interpreted landslides is 1 515 in the west area(WA), which is near to the macro-epicentre, and 2 049 in the east area(EA), respectively. Based on the empirical relationship between the landslide volume and area, we get the estimated landslide volume of 2.85~6.40km³ of WA and EA, which is equivalent or bigger than the value of ~2.8km³ caused by Wenchuan earthquake of M_W7.9 on 12^th May 2008. These earthquake triggered landslides are the main cause for the death of inhabitants living in houses or loess house caves located outside of the basin, such as Weinan, Lintong, Lantian(affected by WA) and Lingbao(affected by EA). Our results can help deeply understand the distribution characteristics of coseismic disaster of the 1556 Huaxian earthquake to the south of Weihe Basin, and also provide important reference for the modification of the isoseismals.

LATE QUATERNARY ACTIVITY AND PALEOSEISMIC RUPTURE BEHAVIOR FOR THE SOUTHEAST SECTION OF THE GANZI-YUSHU FAULT

WANG Ming-ming, HE Yu-lin, LIU Shao, WANG Shi-yuan, MA Chao, ZHANG Wei, JIA Zhao-liang

2018, 40(4):  738-752.  DOI: 10.3969/j.issn.0253-4967.2018.04.002

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The Ganzi-Yushu Fault, the boundary of Bayan Har active tectonic block, Qiantang active tectonic block and Sichuan-Yunan active tectonic block, is a sinistral strike-slip fault zone with intensive Holocene activity. Thus, the study of activity characteristics and rupture behavior of paleoearthquakes in the late Quaternary on the Ganzi-Yushu Fault is of fundamental importance for understanding the future seismic risk of this fault. The southeast section of Ganzi-Yushu Fault is made up of three segments of Ganzi, Manigange and Dengke, where a M_S7.3 earthquake in 1866, a M_S7.7 earthquake in 1854 and a M_S7.3 in 1896 occurred, respectively. There is still lack of in-depth study on the active features and the cascading rupture possibility of these segments, which hindered the evaluation of seismic risk for the southeast section of Ganzi-Yushu Fault. By the means of field geological survey and micro topography measurement, this paper studied the geological and geomorphological features of the southeast section of the Ganzi-Yushu Fault. The results show that the Ganzi and Dengke segments show obvious extension movement, in addition to the left-lateral movement. For Manigange segment, the characteristics of the movement are mainly left-lateral strike-slip and thrusting, and the maximum vertical displacement of the Holocene strata is greater than 2m. In part areas, the movement is normal faulting, which perhaps relates to the left stepping zone in the local stress environment. Therefore, combining the research results such as the fracture distribution in different motion characteristics, rupture behavior of paleoearthquakes, and the distribution of historical earthquake surface ruptures, we divide the southeast section of Ganzi Yushu Fault into Ganzi, Manigange and Dengke segment, and consider the Yakou and the Dengke Basin as the stepovers and the segments' boundaries. As the small scale of impermanent barriers including Dengke Basin and the ridge near Yakou, of which the width is about 1~2km, they may be broken through in great earthquake rupture in future. A trench was excavated in Zhuqing township to investigate the paleoearthquakes on the Manigange segment, radiocarbon dating was employed and 3 paleoseismic events were revealed in the Zhuqing trench, which are the seismic events occurring respectively at 3875~3455BC, after 775BC, and the latest one that ruptured the surface. Compared with the previous results of paleoseismology in the southeast section of Ganzi-Yushu Fault, it is found that the paleoseismic events in the Manigange segment are obviously different with that in Ganzi segment and Dengke segment. Due to the lack of sufficient data on the southeast section of the Ganzi-Yushu Fault, it still needs further discussion whether the cascade-rupturing between these segments exists.

STUDY ON PALEOEARTHQUKES ALONG THE FODONGMIAO-HONGYAZI FAULT, GANSU PROVINCE

HUANG Xiong-nan, YANG Xiao-ping, YANG Hai-bo

2018, 40(4):  753-772.  DOI: 10.3969/j.issn.0253-4967.2018.04.003

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The Fodongmiao-Hongyazi Fault is a Holocene active thrust fault, belonging to the middle segment of northern Qilianshan overthrust fault zone, located in the northeastern edge of the Tibet plateau. The Hongyapu M7(1/4) earthquake in 1609 AD occurred on it. A few paleo-seismology studies were carried out on this fault zone. It was considered that four paleoearthquakes occurred on the Fodongmiao-Hongyazi Fault between(6.3±0.6) ka BP and(7.4±0.4) ka BP, in(4.3±0.3) ka BP, in(2.1±0.1) ka BP and in 1609 AD. The occurrences of the earthquakes suggested the quasi-periodic characteristic with a quasi-periodic recurrence interval between 1 600~2 500a(Institute of Geology, State Seismological Bureau, Lanzhou Institute of Seismology, State Seismological Bureau. 1993; Liu et al., 2014). There was no direct evidence for the Hongyapu M7(1/4) earthquake in 1609 AD from trench research in the previous studies. Great uncertainty exists because of the small number of the chronology data, as a few TL and OSL measurement data and several¹⁴ C data, and it was insufficient to deduce the exact recurrence interval for the paleoearthquakes.
Five trenches were excavated and cleared up respectively in the eastern segment, middle segment and western segment along the Fodongmiao-Hongyazi Fault. After detail study on the trench profiles, the sedimentary characteristics, sequence relationship of the stratigraphical units, and fault-cuts in different stratigraphical units were revealed in these five trenches. Four paleoearthquakes in Holocene were distinguished from the five trenches, and geology evidences of the Hongyapu M7(1/4) earthquake in 1609 AD were also found.
More accurate constraint of the occurring time of the paleo-earthquakes since Holocene on the Fodongmiao-Hongyazi Fault is provided by the progressive constraining method(Mao and Zhang, 1995), according to amounts of ¹⁴ C measurement data and OLS measurement data of the chronology samples from different stratigraphical units in the trenches. The first paleoevent, E4 occurred 10.6ka BP. The next event, E3 occurred about 7.1ka BP. The E2 occurred about 3.4ka BP. The last event, E1 is the Hongyapu M7(1/4) earthquake in 1609 AD.
Abounds of proofs for the occurrences of the events of E1, E2 and E3 were found in the trench Tc1, trench Tc2, trench Tc4 and trench Tc3, located in the eastern, middle and western segments of the Fodongmiao-Hongyazi Fault accordingly. It's considered that the events E1, E2 and E3 may cause whole segment rupturing according to the proofs for these three events found together in individual trenches. The event E4 was only found in the trench Tc5 profile in the west of the Xiaoquan village in the eastern segment of the Fodongmiao-Hongyazi Fault. The earthquake rupture characteristics of this event can't be revealed before more detailed subsequent research.
The time intervals among the four paleoearthquakes are ca 3.5ka, ca 3.7ka, and ca 3.0ka. The four events are characterized by ca 3.4ka quasi-periodic recurrence interval.

RESEARCH ON THE MOTION PATTERN OF SLIP-STRIKE FAULT BY USING DEFLECTION ANGLES——A CASE STUDY OF THE NANTINGHE FAULT

SHI Feng, HE Hong-lin, Alexander L Densmore, WEI Zhan-yu, SUN Hao-yue

2018, 40(4):  773-783.  DOI: 10.3969/j.issn.0253-4967.2018.04.004

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Since the 1970s, active tectonics has advanced from qualitative research to quantitative research. Many researchers focus on which qualitative parameters to obtain and how to obtain them. It is usually accepted that the following parameters are necessary for quantitative descriptions of active faults:length of a fault or segment, displacements, slip rates, and paleo-earthquake events. Because of the complex nature of problems concerned and limited capability of human recognition, there are still some errors and uncertainties in these parameters. Tectonic geomorphology provides a useful tool to help solve the problems above. Tectonic geomorphology could record long-term accumulation of tectonics, and quantize them by relevant parameters. Tectonic movements have been exerting significant influence upon formation of topography and landforms, and such processes are usually extremely slow over very long time which cannot be documented by human history and any instruments. Observations, especially direct measurements of various features of geomorphology can reveal details of tectonic movement, including slip on active faults. In the early time, such studies were usually limited in one or two parameters of geomorphology to characterize active tectonics. With rapid development of computer and DEM technologies, it is possible to use multiple parameters of landforms to describe regional tectonic activity. Previous work in this aspect focused on large scales, while a little on small scale faults or individual faults. And existing studies are mostly concerned with normal or thrust faults dominated by vertical motion. In this paper, we focus on the Nantinghe Fault, which is strike-slip fault. Based on high resolution DEM extracted from ALOS data, we extract 180 drainages along the Nantinghe Fault. Based on the relationship between deflection angles and faulting, we analyze the segmentation and activity. Using the distribution patterns of the factors, this study examines the geometry and activity of the Nantinghe Fault, which were obtained from comprehensive remote sensing interpretation and field investigations. The results provide an example for research on the relationship between faulting and landforms.

A PRELIMINARY RESEARCH ON THE RIGHT-LATERAL STRIKE-SLIP CHARACTERISTICS AND THE STRUCTURAL SIGNIFICANCE OF THE NORTHERN KUANTANSHAN FAULTS, HEXI CORRIDER, BASED ON HIGH-RESOLUTION IMAGERY

GUO Chang-hui, LI An, LIU Rui, ZHANG Shi-min

2018, 40(4):  784-800.  DOI: 10.3969/j.issn.0253-4967.2018.04.005

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The sinistral strike-slip characteristic of the Altyn Tagh Fault gradually disappears near the Jiuxi Basin at the west end of Hexi Corridor, and the Kuantanshan Fault and the northern marginal fault of Heishan on its east are thrust structures. There are two faults distributed in the north of Kuantanshan, namely, the Taerwan-Chijiaciwo Fault and the Ganxiashan Fault, both are featured with obvious activity. Predecessors thought that the Taerwan-Chijiaciwo Fault is a thrust fault with low movement rate, but there is few detailed study on its horizontal motion. Is there horizontal strike-slip movement in the northern marginal fault of Kuantanshan? This issue has an important significance to further explore the structural transformation mode between the Altyn Tagh strike-slip faults and the northern thrust faults in the north margin of Qilianshan. Using high resolution remote sensing images and field work, such as combining with UAV SfM photogrammetry, the paper studies the strike-slip characteristics of the Taerwan-Chijiaciwo Fault and Ganxiashan Fault on the northern margin of Kuantanshan, and get two preliminary understandings:(1) The northern marginal fault of Kuantanshan is an active right-lateral strike-slip fault with thrust component, the horizontal to vertical dislocation ratio is about 3-4 times. Based on the statistics of dislocation amount of the gullies and terraces along the north marginal Kuantanshan fault, it is preliminarily estimated that the late Pleistocene right-lateral strike-slip rate is about 0.2-0.25 mm/a and the Holocene right-lateral strike-slip rate is about 0.5-1.5 mm/a. (2) The main driving force to the tectonics at the western end of Hexi Corridor, where the northern marginal fault of Kuantanshan locates, comes from the northward extrusion of the Qilian Mountains, which results in the right-lateral strike-slip of the northern marginal fault of Kuananshan and the thrust movement of several faults inside the Jiuxi Basin. The effect of the Altyn Tagh Fault on other tectonic structures is not obvious in this region.

PRELIMINARY STUDY OF PALEOEARTHQUAKES ON THE MIDDLE-EASTERN SEGMENT OF JINTA NANSHAN FAULT

PANG Wei, ZHANG Bo, HE Wen-gui, WU Ming

2018, 40(4):  801-817.  DOI: 10.3969/j.issn.0253-4967.2018.04.006

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Hexi Corridor is located at the northeastern margin of the Tibetan plateau. Series of late Quaternary active faults are developed in this area. Numerous strong earthquakes occurred in history and nowadays. Jinta Nanshan fault is one of the boundary faults between the Qinghai-Tibet block and the Alxa block. The fault starts from the northwest of Wutongdun in the west, passes through Changshan, Yuanyangchi reservoir, Dakouzi, and ends in the east of Hongdun.
Because the Jinta Nanshan fault is a new active fault in this region, it is important to ascertain its paleoearthquakes since late Pleistocene for the earthquake risk study. Previous studies were carried out on the western part, such as field geomorphic investigation and trench excavation, which shows strong activity in Holocene on the western segment of Jinta Nanshan fault. On the basis of the above research, in this paper, we carried out satellite image interpretation, detailed investigation of faulted landforms and differential GPS survey for the whole fault. Focusing on the middle-eastern part, we studied paleoearthquakes through trench exploration on the Holocene alluvial fan and optical luminescence dating.
The main results are as follows:Early Pleistocene to late Pleistocene alluvial strata are widely developed along the fault and Holocene sediment is only about tens of centimeters thick. The Jinta Nanshan fault shows long-lasting activity since late Quaternary and reveals tens of centimeters of the lowest scarp which illustrates new strong activity on the middle-east segment of this fault. Since late Pleistocene, 4 paleoearthquakes happened respectively before(15.16±1.29) ka, before(9.9±0.5) ka, about 6ka and after(3.5±0.4) ka, revealed by 4 trenches, of which 2 are laid on relatively thicker Holocene alluvial fan. Two events occurred since middle Holocene, and both ruptured the whole fault.

THREE-DIMENSIONAL DEFORMATION CHARACTERISTICS OF THE XIANSHUIHE FAULT ZONE

ZHAO Jing, REN Jin-wei, JIANG Zai-sen, Yue Chong

2018, 40(4):  818-831.  DOI: 10.3969/j.issn.0253-4967.2018.04.007

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In order to analyze 3-dimensional movement and deformation characteristics and seismic risk of the Xianshuihe fault zone, we inverted for dynamic fault locking and slip deficit rate of the fault using the GPS horizontal velocity field of 1999-2007 and 2013-2017 in Sichuan-Yunnan region, and calculated annual vertical change rate to analyze the vertical deformation characteristics of the fault using the cross-fault leveling data during 1980-2017 locating on the Xianshuihe fault. The GPS inversion results indicate that in 1999-2007, the southeastern segment of the fault is tightly locked, the middle segment is less locked, and the northwestern segment is basically in creeping state. In 2013-2017, the southeastern segment of the fault is obviously weekly locked, in which only a patch between Daofu-Bamei is locked, and the northwestern segment is still mostly in creeping state, in which only a patch at southeastern Luhuo is slightly locked from surface to 10km depth. The cross-fault leveling data show that annual vertical change rate of the Zhuwo, Gelou, Xuxu and Goupu sites on the northwestern segment is larger, which means vertical movement is relatively active, and annual vertical change rate of the Longdengba, Laoqianning, and Zheduotang sites on the southeastern segment is small, which means the fault is locked, and the vertical movement changes little before and after the Wenchuan earthquake. Combining with the 3-dimensional movement and deformation, seismic activity and Coulomb stress on the Xianshuihe Fault, we consider the seismic risk of the southeastern segment is larger, and the Wenchuan earthquake reduced the far-field sinistral movement and the fault slip deficit rate, which may reduce the stress and strain accumulation rate and relieve the seismic risk of the southeastern segment.

TECTONIC INDICATIONS OF OCCURRENCE OF MODERATE-TO-STRONG EARTHQUAKES IN CHAOHU-TONGLING AREA, ANHUI PROVINCE

GUO Peng, HAN Zhu-jun, ZHOU Ben-gang, ZHOU Qing, MAO Ze-bin

2018, 40(4):  832-849.  DOI: 10.3969/j.issn.0253-4967.2018.04.008

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The Chaohu-Tongling area in Anhui Province is a typical moderate-to-strong earthquake active area in the mainland of China. Four earthquakes occurred in this area, displayed as a NNE-trending zonal distribution, including the 1585 M5(3/4) Chaoxian earthquake and the 1654 M5(1/4) Lujiang earthquake, which formed a striking moderate-to-strong seismic activity zone. Field survey, shallow geophysical prospecting, drilling data, collection and dating of chronology samples and comprehensive analysis of fault activity indicate that the Fanshan, Xiajialing and Langcun faults are not active since Quaternary. The NNE-trending Tongling Fault is a buried middle-Pleistocene fault, but it can produce moderate-to-strong earthquakes and control the evolution and development of three en echelon geologic structures. The intensity of the four earthquakes is characterized by southward progressive decrease, which is in accordance with the characteristics that the subsidence range of Wuwei Basin is obviously larger than that of Guichi Basin to its south since late Cenozoic. In terms of deep structure, the characteristics of spatial distribution of Tongling Fault indicate that it corresponds to a NNE-striking Bouguer gravity anomaly gradient belt. So there is a spatial correspondence between the middle-Pleistocene Tongling Fault, the en echelon structures, the differential movement of the neotectonics, the Bouguer gravity anomaly gradient belt and the moderate-to-strong seismic activity belt in the Chaohu-Tongling area, indicating that they should be the tectonic indications of occurrence for moderate-to-strong earthquakes.

SIMULATION OF STRONG GROUND MOTION IN AKETAO M6.7 EARTHQUAKE USING THEORETICAL GREEN'S FUNCTION

FENG Wei, LIU Jie, LUO Jia-hong, HOU Jian-sheng

2018, 40(4):  850-860.  DOI: 10.3969/j.issn.0253-4967.2018.04.009

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Aketao M6.7 earthquake on November 25, 2016 occurred in Aketao Country, Kizilsu Kirghiz Autonomous Prefecture, Xinjiang Autonomous Region. In this paper, according to the focal mechanism solution, the geometrical parameters of the fault are used as input to simulate the acceleration records of the surrounding area of Aketao M6.7 earthquake on November 25, 2016 with the QSGRN/QSCMP program. The peak ground acceleration distribution is plotted by extracted peak ground accelerations and site condition correction. Comparison is carried out between the observed waveforms and the simulated waveforms in the time domain and the frequency domain of two strong motion stations. It is verified that the amplitudes of simulated and observed data are equal in magnitude, their calculated residuals are smaller in low frequency range and the spectral characteristics of simulated and observed data are consistent. Furthermore, the simulated peak ground acceleration corresponding to the coordinates of the actual survey points is extracted and compared with the survey spot intensity, and both have good correspondence. This paper attempts to provide a method for rapid output of peak ground acceleration distribution after an earthquake, so as to provide a method for estimating the seismic impact field in areas where the monitoring station is scarce, the topography is complex or it is difficult to implement the rapid earthquake disaster investigation. And it also provides supporting information for rapid assessment of earthquake disaster and emergency decision-making.

STUDY OF THE INFLUENCE OF STRONG EARTHQUAKE ON THE RECURRENCE BEHAVIOR OF MAJOR EARTHQUAKE ON ACTIVE FAULT-TAKING THE MIDDLE-NORTH SECTION OF XIANSHUIHE FAULT AS AN EXAMPLE

HUI Chun, PAN Hua, XU Jing

2018, 40(4):  861-871.  DOI: 10.3969/j.issn.0253-4967.2018.04.010

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It is of great significance to determine the factors and causes that affect the recurrence of major earthquakes. This paper introduces the influence of strong earthquake on the recurrence of major earthquakes according to elastic rebound theory, and then proposes to calculate the impact time Δt respectively from the effect of strong earthquakes on the same and surrounding faults on the major earthquake recurrence by using seismic moment release rate method and Coulomb stress change. In this paper, we studied the change amount of major earthquake recurrence by taking four earthquakes with magnitude greater than 6.5 occurring at different fracture sections of the Xianshuhe fault zone as an example, they occurred on Daofu, Changcu, Zhuwo Fault, respectively. We used seismic moment rate method to calculate the impact time Δt of strong earthquake on the recurrence of major earthquakes on the Daofu-Qianning Fault. We further discussed the effect of the Coulomb stress change due to the interaction between faults on the recurrence of subsequent major earthquakes. The co-seismic and post-seismic Coulomb stress changes caused by strong earthquake on the surrounding faults on the Ganzi-Luhuo Fault are calculated. With the fault interaction considered, the importance of the interaction between faults in the middle-north section of the Xianshuihe fault zone to change the recurrence of large earthquakes is retested and evaluated. The results indicate that the two strong earthquakes occurring along Xianshuihe Fault in 1904(M=7.0) and 1981(M=6.9) resulted in a delay of 80 years and 45 years of major earthquake recurrence on the Daofu-Qianning Fault respectively, and the M7.3 earthquake in 1923 and the M6.8 earthquake in 1967 resulted in an advance of 35 years of major earthquake recurrence on the Ganzi-Luhuo Fault.

STUDY ON THE SEISMOGENIC FAULT CHARACTERSTICS OF 2016 M_W5.9 MENYUAN EARTHQUAKE BASED ON Sentinel -1A DATA

ZHENG Bo-wen, GONG Wen-yu, WEN Shao-yan, ZHANG Ying-feng, SHAN Xin-jian, SONG Xiao-gang, LIU Yun-hua

2018, 40(4):  872-882.  DOI: 10.3969/j.issn.0253-4967.2018.04.011

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In this paper, we processed and analyzed the Sentinel-1A data by "two-pass" method and acquired the surface deformation fields of Menyuan earthquake. The results show the deformation occurred mainly in the south wall of fault, where uplift deformation is dominant. The uplift deformation is significantly larger than the subsidence and the maximum uplift of ascending and descending in the LOS is 6cm, 8cm respectively. Meanwhile, based on the Okada model, we use the ascending and descending passes data as constraints to invert jointly the fault distribution and source parameters through constructing fault model of different dip directions. The optimum fault parameters are:The dip is 43°, the strike is 128°with the mean rake of 85°. The maximum slip is about 0.27m. The inverted seismic moment M₀ is 1.13×10¹⁸N·m, and the moment magnitude M_W is 5.9. The SW-dipping Minyue-Damaying Fault is possibly the seismogenic fault, based on the comprehensive analysis of the focal mechanisms, aftershocks relocation results and the regional tectonic background. The focus property is dominated by thrust movement with a small amount of dextral strike-slip component. The earthquake is the result of local stress adjustment nearby the Lenglongling Fault under the background of northeastward push and growth of Tibet Plateau.

A STUDY ON THE SEISMOGENIC STRUCTURE OF LINFEN M7(3/4) EARTHQUAKE IN 1695

YAN Xiao-bing, ZHOU Yong-sheng, LI Zi-hong, GUO Jin

2018, 40(4):  883-902.  DOI: 10.3969/j.issn.0253-4967.2018.04.012

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A magnitude 7(3/4) earthquake happened in Linfen, Shanxi, on May 18, 1965(the 34th year of Qing Emperor Kangxi). In the Catalogue of Chinese Historical Strong Earthquakes, the epicenter of this earthquake is located at the northwest of Zhangli Village of Xiangfen County and Dongkang Village of Yaodu District, Linfen City(36.0°N, 111.5°E), and the epicentral intensity is Ⅹ. It was inferred by previous studies that Guojiazhuang Fault is the seismogenic structure of the earthquake. In this paper, in cooperation with the Archives of Linfen City and Earthquake Administration of Linfen, the author looked up in details the first-hand materials of the earthquake damage to the ancient town of Linfen and its surrounding areas, and based on this, drew the isoseismals of the earthquake. Through discussions with relevant experts, we consider that it would be more appropriate that the location of the macroscopic epicenter of this earthquake is in Donguan area of the ancient town of Linfen, the epicentral intensity is Ⅺ, and the major axis of the isoseismals is in NWW. Later, in the implementation of "Linfen city active fault detection and seismic risk evaluation", we found two earthquake fault outcrops near the macroscopic epicentral area of the 1695 Linfen earthquake. Shallow seismic exploration lines and drill rows perpendicular to the strike of the fault outcrops were arranged to implement the exploration. The results demonstrate that the right-lateral stepover composed of Guojiazhuang Fault and Liucun Fault, together with the Luoyunshan Fault(Longci segment), were involved in the 1695 Linfen earthquake, the intersection of the faults is the microscopic epicenter of the earthquake, and the above-mentioned three faults are the seismogenic structure of the earthquake. In addition, the seismic geological remains in this region(landslides, earthquake ground cracks, sand emitting channels, etc.) are mainly distributed on the hanging wall of the Guojiazhuang Fault, this proves from another perspective that the earthquake remains is the product of activity of Guojiazhuang Fault in 1695.

MICROSTRUCTURAL FEATURES AND IMPLICATIONS OF FAULT GOUGE FROM THE FAULTS OF BEDROCK REGION IN THE CENTRAL-NORTHERN JIANGXI PROVINCE, CHINA

HAN Zhu-jun, ZHANG Bing-liang, ZENG Xin-fu, LU Fu-shui, GUO Peng

2018, 40(4):  903-919.  DOI: 10.3969/j.issn.0253-4967.2018.04.013

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How to survey fault activity and determine seismogenic structures in a relatively stable and bedrock-distributed region is a challenging research work. Ruichang-Tonggu Fault and Yifeng-Jingdezhen Fault, distributed mainly at the pre-Cenozoic bedrock region, show the geological evidences of activity in the Quaternary and they are two important tectonic belts for the occurrence of moderate earthquakes in the central-northern Jiangxi Province. Fault gouge stripes can be found on the outcrop sections of the two faults. The imageries of the microstructures of fault gouge show abundant phenomena about the structural deformation, and it is clear that the fault gouge was formed by structural activity. As to the deformation modes, there are not only the Y-shears and R1-shears, which represent the localized-brittle deformation, but also the P-foliations, which reflect the ductile deformation in the microstructures of fault gouge. These features demonstrate that the micro-scale rapid deformation can exist in the seismogenic structure at the near-surface in the occurrence process of moderate earthquakes very possibly. The microstructures of soft material from the fault outcrop section at the southern segment of Hukou-Xingan Fault, which is inactive in the Quaternary, reflects that the soft material from the fault zone can also be the products of rainwater leaching and filling, or weathering in the later periods. Based on the macroscopic observation in the field, it is sometimes difficult to distinguish the differences of structurally-formed or non-structurally formed soft gunk in the fault zones, however, their differences in the microstructure on the slices grinded indoor are obvious. The relatively stable bedrock areas in South China often are not only favorable for the siting of major projects, such as nuclear power plant in China, but also the economically-developed, densely populated, urban agglomeration areas. The study of microstructure of fault gouge provides a technical reference approach for the identification of fault activity and the determination of seismogenic structure of moderate-strong earthquakes in assessing the seismotectonic environment in these regions.

A NEW METHOD FOR COLOR MEASUREMENT OF QUATERNARY DRILLING CORE DEPOSITS

HE Fu-bing, XU Xi-wei, ZHENG Gui-sen, SUN Yong-hua, ZHANG Wei, LI Li, LI Rui-jie

2018, 40(4):  920-934.  DOI: 10.3969/j.issn.0253-4967.2018.04.014

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In this paper, a method for measuring the color of Quaternary sediments based on digital image analysis is proposed, which has the advantages of simple and quick operation, and improving the research efficiency of sediment color. In order to demonstrate the feasibility of this method, the measurement results are compared with the traditional colorimetric measurement methods. The results show that:1) Both the traditional sediment color measurement method and the digital image color measurement method are controlled by sediment grain size. Sediment color research can be carried out on fine sand or finer sediments, but for medium grained sand and coarse sand, the error will be larger. Compared with the traditional measurement methods, digital image method can reduce the inherited color interference of coarse clastic sediments; 2) The particle size and water content of clastic sediments affect the numerical value of digital image sediment color. Generally, the wet-color values obtained by the digital image method are lower than the dry-color values obtained by using a spectrophotometer, and the color value variation is large, and the undulation of chromaticity/brightness curve is greater; 3) Compared with the traditional sediment color measurement method, digital image method has good consistency of color measurement of redness and yellowness, but the brightness is affected by uneven illumination, resulting in some error. Sediment digital image extraction of sediment color information can replace the indoor measurement method to a certain extent, and can be used to establish a more complete sediment color sequence under more complex sedimentary environment, so as to provide information for the Quaternary stratigraphic division, paleoclimate research, paleosol recognition and paleoearthquake event identification, thus expanding the application of colorimetric results to the geological direction.

A PRELIMINARY STUDY ON THE CORRELATIVITY OF SEISMIC HAZARD BETWEEN BEIJING AREA AND XIONG'AN NEW AREA

WU Qing, GAO Meng-tan

2018, 40(4):  935-943.  DOI: 10.3969/j.issn.0253-4967.2018.04.015

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Xiong'an New Area is established on April 1, 2017 and some non-capital functions from Beijing would be transferred to this new area. As a political, economic, and cultural center of China, Beijing has a highly dense population, buildings, and transportation. With the rapid development of the urban economy, the population and assets exposed to dangerous areas with M ≥ 7 earthquakes have accumulated in an exponential manner, leading to a continuous surge in seismic risk in Beijing. Studying on the correlativity of seismic hazard between Beijing area and Xiong'an New Area is of great significance to judge whether Xiong'an can play a role in the dispersal of seismic risk of Beijing. Using Monte Carlo method to simulate synthetic earthquake sequences, and for each simulated earthquake, the peak ground acceleration data sets on each site of Beijing and Xiong'an can be calculated through the attenuation relationship. Based on the statistical analysis of the ground motion peak acceleration data sets, this paper holds that the correlativity of the ground motion between Beijing area and Xiong'an New Area is not high; the probability of Beijing and Xiong'an suffering at the same time from an exceeded fortification level of ground motion effect is very low; the probability of Beijing and Xiong'an suffering at the same time from a rare ground motion effect is extremely low. Through defibering population, assets, and setting up a remote backup of earthquake emergency equipment and supplies, Xiong'an New Area can disperse the high seismic risk of Beijing to some extent.