Underestimated seismic hazard in the south of the Issyk-Kul Lake region (northern Tian Shan)

The Tian Shan Mountains were formed in the result of the India-Eurasia collision, which leads to cre- ation of contrast high-mountain relief and world known seismic activity. The seismic catastrophes, recorded instrumentally, have occurred to the north of the Issyk-Kul Lake region. There are also known significant earthquakes with magnitude being about 7 in western and eastern parts of the mentioned lake region. Only in the south of the Issyk-Kul depression the strong earthquakes recorded by the seismic network were not known. Our recent study in the south of the lssyk-Kul Lake region has revealed numerous active tectonic structures related to South Issyk-I（ul Fault： faults and folds, responsible for strong earthquakes＇ occurrence. These were historical and paleoseismic defornlations which led to changes in relief： fault scarps and significant rockslides. We have also found spectacular deformations in archeological monuments. All these deformations testify the location of epicentral areas of two strong historic （about llth and 16th （？） centuries AD） and paleoearthquakes （Holocene and Late Pleistocene）. Magnitude of ancient seismic events, according to parameters of the revealed fault scarps, were Ms 〉 7 and seismic intensity I 〉 IX. All revealed seismic deformations are located to adyrs （piedmonts） of the Terskey Ala-Too range bordered of the lssyk-Kul Lake depression in the south. Their formation is described by the model of a fault which rupture plane becomes shallower southward. This model is complicated by the presence of reverse thrusts. Here, we should admit the existence of a single zone of South lssyk-Kul Fault which is a long-lived feature which separates the structures with the different regime of movements during the Neotectonic time. All obtained data led us to a conclusion of significant underestimation of the seismic hazard in southern lssyk-Kul Lake region.

Evolution of landscape in a piedmont section of Eastern Himalayan foothills along India-Bhutan border: A tectono-geomorphic perspective

The present study area involves part of a deformed coalesced fan located along the Himalayan Frontal Thrust(HFT)on the east of river Tista near the India-Bhutan border.The area is marked by two spectacular E-W trending south-sloping scarps namely the Matiali(ca.60 m)and Chalsa(ca.90 m)Scarps and a north-sloping E-W trending Thaljhora(ca.80 m)Scarp.Our work comprises of a comparative study of geomorphology and geologic history in the adjacent interfluves of Jaldhaka-Gathia and Neora-Murti rivers to understand the tectonic history of the area.We mapped the Jaldhaka-Gathia river interfluve at a 1:25,000 scale and report a hitherto unidentified northerly sloping small scarp of ca.5 m height named the Nagrakata Scarp.This scarp was identified using satellite images,DEMs,and total station survey.We interpret that the two northsloping,E-W trending scarps(Thaljhora and Nagrakata Scarps)are manifestations of steep limbs of anticlines over blind south-dipping back thrusts.Together they form a wrinkle-ridge pair behind the north-dipping HFT,which is manifested by south-sloping Chalsa Scarp.We propose a plausible geomorphic model interpreting that deformation along the small fan in the Jaldhaka-Gathia interfluves is younger compared to fan deposition and deformation in the adjacent Mal-Murti interfluve.The most recent geomorphology of the Jaldhaka-Gathia interfluve is controlled by tectonism associated with the thrust below the Nagrakata Scarp where the youngest deformation episode is recorded to at around^6 ka and is likely related to motion on a splay off of the thrust beneath the Thaljhora Scarp.

Studies on the Surface Rupture Zone of 1303 Hongdong Earthquake of M =8 and Paleoearthquakes of Huoshan Fault in Shanxi Province

An earthquake of M=8 occurred in the Linfen Basin of the Shanxi graben system in 1303,producing a surface rupture zone about 45km long.Compiling a geological map at 1:10,000 and studying in detail the rupture zone,its dextral strike-slip displacement is determined to be 4-8.6 m,and normal dip-slip displacement up to 3.5-5 m.In this paper the geochronological evidence for the formation of the surface rupture zone is provided and the Huoshan fault is confirmed to be the seismogenic structure for the M=8 earthquake.Field trenching enables us to identify two paleoseismic events having occurred along the Huoshan fault since the middle Holocene before the M8 earthquake.A recurrence interval of these three events including 1303 Hongdong M 8 earthquake is determined to be up to 1500-2000 years.The result corresponds to the mean recurrence interval calculated from slip rate on the Huoshan fault during Holocene.

Seismogenic Structure of the 1411 Southern Damxung (Damdoi) Earthquake with M=8 in Tibet

The seismogenic structure of the 1411 southern Damxung(Damdoi)earthquake with M=8 in Tibet is discussed in detail in this paper.It is pointed out that the Nyainqentanglha southern pediment fault is the seismogenic one of the 1411 southern Damxung(Damdoi)earthquake with M=8,and the macroepicenter is located at the intersection of the extensional shear fault within Nasego-Garbogo pull-apart basin and the secondary strike-slipping fault with larger amplitude of neotectonic activity at the southwestern side of the basin.Besides,there is obvious anomaly of the geophysical fields in the seismic area,indicating that occurrence of 1411 southern Damxung(Damdoi)earthquake with M=8 was not only controlled by the superstructure but also the background of deep-seated structure.

Calculation of reverse-fault-related parameters using topographic profiles and fault bedding

Fault-related parameters are critical for studying tectonic evolution, deformation character- istics, active tectonism, and seismic hazards. A new method of calculating reverse-fault- related parameters has been developed, which uses systematic analysis of the geometrical characteristics of normal and reverse scarps of reverse faults together with measurements of topographic profiles and fault bedding. The results show that the most suitable method of calculating fault parameters heavily relies on the specific type of fault scarp. For a reverse scarp, the size of the vertical displacement （VD） of the fault, the vertical separation （VS） of the hanging wall and the footwall, and the fault scarp height （SH）how the relationship VD ≥VS ≥ SH; conversely, for normal scarps, VD ≤ VS ≤ SH. The theoretical equations were used to study fault deformation in the Southwest Tianshan Mountain foreland basin. The results showed that, for every fault, VD ≥ VS ≥SH, which is consistent with our predicted relationship. This finding demonstrates that this method is suitable to explore structural information of reverse faults. In the study area, the vertical displacement is 1.4 times the horizontal displacement, suggesting that fiexural-slip faults may play an important role in transferring local deformation from horizontal shortening to vertical uplift. Therefore, one of the most important steps in correct calculation of reverse-fault-related parameters is selection of the proper equations by identifying the specific type of fault scarp and the corresponding calculation method.

Impact of long term uplift on stream networks in tectonically active Northern Hill Range, Kachchh palaeo-rift basin, western India

The study deals with stream response to sustained tectonic during the Cenozoic and development of two parallel scarps in the western Kachchh. The study encompasses fluvial networks developed over the Jara and Jumara domes, which are a part of the laterally extensive belt of flexures bounded by the Kachchh Mainland Fault(KMF) to their north and called as Northern Hill Range(NHR). Parameters such as longitudinal profile, Hack profile, stream length gradient index(SL), hypsometric curve, hypsometric integral(HI), valley floor width to height ratio(Vf), elongation ratio(Re) and escarpment sinuosity(ES) were analysed. Hack profiles of the major rivers draining through the area show similar convex up nature suggesting primary influence of the tectonics in controlling and shaping the landscape of the region. Elongation ratio <6 and undergone higher degree of fluvial erosion indicated by the low values of hypsometric integral suggest the tendency of river systems to increase the basin area longitudinally rather than laterally. The study suggests that higher net uplift in the eastern half(Jumara dome) caused the rivers to overcome the structural control and to carve out generally straight north oriented channels. The rivers of western part(Jara dome) show more prominent structural control of cuesta girdles formed in compact lithologies and attributed to the domal structure. The ~10 km long Jaramara scarp believed to the remnant of older KMF scarp, is a product of headward erosion of the fluvial channels through different hard and soft litho-units of the area. The similar orientation of Jaramara scarp and morphology of the Ukra intrusive body suggests that the Ukra intrusive played a significant role in controlling the formation and morphology of the Jaramara scarp.

Recognition of Fluvial Bank Erosion Along the Main Stream of the Yangtze River

Recognizing the risk of fluvial bank erosion is an important challenge to ensure the early warning and prevention or control of bank collapse in river catchments,including in the Yangtze River.This study introduces a geomorphons-based algorithm to extract river bank erosion information by adjusting the flatness from multibeam echo-sounding data.The algorithm maps ten subaqueous morphological elements,including the slope,footslope,flat,ridge,peak,valley,pit,spur,hollow,and shoulder.Twentyone flatness values were used to build an interpretation strategy for the subaqueous features of riverbank erosion.The results show that the bank scarp,which is the erosion carrier,is covered by slope cells when the flatness is 10°.The scour pits and bank scars are indicated by pit cells near the bank and hollow cells in the bank slope at a flatness of 0°.Fluvial subaqueous dunes are considered an important factor accelerating bank erosion,particularly those near the bank toe;the critical flatness of the dunes was evaluated as 3°.The distribution of subaqueous morphological elements was analyzed and used to map the bank erosion inventory.The analysis results revealed that the near-bank zone,with a relatively large water depth,is prone to form large scour pits and a long bank scarp.Arc collapse tends to occur at the long bank scarp to shorten its length.The varied assignment of flatness values among terrestrial,marine,and fluvial environments is discussed,concluding that diversified flatness values significantly enable fluvial subaqueous morphology recognition.Consequently,this study provides a reference for the flatness-based recognition of fluvial morphological elements and enhances the targeting of subaqueous signs and risks of bank failure with a range of multibeam bathymetric data.

Activity Feature of Kazkeaerte Fault Zone in the Late Quaternary

Kazkeaerte fault zone is recognized as an important boundary between Pamir and Tianshan Cenozoic Mountain belts in the west of Tarim Basin. It is an active thrust fault and can be divided into three segments from the west to east: Jilekeroute fault zone, Wuqia earthquake fault zone, Mushi fault zone after geological investigating and mapping along Pamir piedmont. Based on the faulted landform as well as deformation and displacement of young deposit layers, the slip rates of Kazkeaerte fault zone since the late Quaternary are briefly studied. The result shows that the average slip rate of fault is differentiate along different segments.

The ground deformation field induced by a listric thrust fault with an overburden soil layer

The surface deformation field induced by a listric thrust fault with a thick, overburden soil layer is studied in this paper by the finite element method （FEM）. The results show： （a） The maximum slip induced by the buried fault is not located at upper tip of the fault, but below it. （b） The vertical displacement changes remarkably near the fault, forming a fault scarp. With the increase of the soil layer thickness, the height of the scarp is decreased for the same earthquake magnitude. （c） The strong strain zone on the surface is localized near the projection of the fault tip on the ground surface. The horizontal strains in the zone are in tension above the hanging wall and in compression above the foot wall, and the vertical strains in the zone are vice versa, which is favorable for tensile- shear, compression-shear fissures above hanging wall and foot wall, respectively.

Quaternary folding in the south piedmont of central segment of Tianshan Mountains

The Tianshan Mountains are an important active structural belt in the interior of Eurasia. By integrated methods of surface geology survey and interpretation of seismic profiles, we distinguish fold scarps located at the south limb of the Kuqatawu anticline and the north limb of the Dongqiulitag anticline in the Kuqa rejuvenation foreland thrust belt, south piedmont of central segment of the Tianshan Mountains. Fold scarp is a newly found structural phenomenon. Because of the bend of thrust plane and the movement of hanging wall above the thrust plane, the original horizontal deposits of hanging wall and their surface become a monocline structure, resulting from the separating and migration of the active and fixed axial surfaces. Measuring the geometry of fold scarp and using the data of age of the deformed deposits, the crustal shortening rate resulting from the deeply seated subsurface thrust is calculated. The crustal shortening rate reflected by the fold scarp located at the north limb of the

XISHUIDONG CAVE, A PALAEOLITHIC SITE NEWLY DISCOVERED IN THE QINLING MOUNTAINS

Xishuidong, a karst cave developed in marble, is situated in the north of the Qinling Mountains, on the scarp of Donggou Valley on the southern slope of Lushan Peak (34°05’N, 109°25′/). The elevation of the chief entrance of the cave is 825 m a.s.l., 65 m higher than the bottom of the valley. Its surrounding topography is rugged, the valley narrow and deep and gravity geomorphology universal. In the summer of 1981, when investigating karst geomorphology in the Qinling Mountains of

SEISMIC GEOLOGY

20111486 Cao Lingling(Earthquake Administration of Gansu Province,Lanzhou 730000,China);Liu Yaowei Preliminary Study on the Characteristics of Integrated Precursors of Fluid before Strong Earthquakes in Sichuan-Yunnan Region(Journal of Seismological Research,ISSN1000-0666,CN53-1062/P,33(3),2010,p.239-246,6 illus.,7 tables,14 refs)Key words:precursor,Sichuan Province,Yunnan

SEISMIC GEOLOGY

20091465 Cai Xuelin(College of Earth Sciences,Chengdu University of Technology,Chengdu 610059,China);Cao Jiamin Preliminary Study on the 3-D Crust Structure for the Longmen Lithosphere and the Genesis of the Huge Wenchuan Earthquake,Sichuan Province,China(Journal of Chengdu University of Technology,ISSN1671-9727,CN51-1634/N,35(4),2008,p.357-365,8 illus.,39 refs.)Key words:deep-seated structures,large earthquakes,Longmenshan Fracture ZoneBased on a structural analysis of many seismic sounding profiles,there are two fault systems in Longmen collisional orogenic belt,Sichuan Province,China.They are both different obviously and correlative closely.One is shallow fault system composed mainly of brittle shear zones in surface crust,and the other is deep fault system composed mainly of crust-mantle ductile shear zones cutting Moho discontinuity.Based on the result of researching geological structure and seismic sounding profiles,