Evaluation of relative tectonic activity along the Priene-Sazli Fault(Soke Basin,southwest Anatolia):Insights from geomorphic indices and drainage analysis

The West Anatolia Extensional Zone, which has a width of about 300 km, is located within the Alpine-Himalayan belt and is one of the regions with intense seismic activity in the world. The most important geomorphological structures in this area are three main graben structures resulting from regional N-S extension since the Early Miocene. These structures are the E-W trending Büyük Menderes, Kü?ük Menderes, and Gediz grabens. S?ke Basin is located at the SW end of the Büyük Menderes graben. The lineaments which control the NW of S?ke Basin have a length of approximately 40 km and have been defined as the Priene-Sazl? Fault(PSF). The PSF is seismically active, and the last large earthquake(the S?ke-Balat earthquake; Ms: 6.8) was produced on July 16 th of 1955. The ancient city of Priene, which was located in the study area, suffered from destructive earthquakes(in the 4 th century and 2 nd century BC, in the 2 nd century AD, during the Byzantine period and after the 12 th century BC). This study aims to reveal the effect of the PSF on the morphotectonic evolution of the region and the relative tectonic activity of the fault. To this end, it was the first time the stream length gradient index(SL: 130-1303), mountain-front sinuosity(Smf: 1.15-1.96), valley floor height and valley width ratio(Vf: 0.27-1.66), drainage basin asymmetry(AF: 0.15-0.76), hypsometric curve(HC) and hypsometric integral(HI: 0.22-0.86) and basin shape index(Bs: 1.04-5.75) along the mountain front that is formed by the PSF. Using a combination of the mountain-front sinuosity(Smf), valley floor height and valley width ratio(Vf), it is found that the uplift ratio in the region is not less than 0.05 mm/yr and the relative tectonic activity of PSF is high. According to the relative tectonic activity index(Iat) obtained from geomorphic indices, the southwest part of the PSF is relatively more active than the northeast part. As a result, I posit that the PSF has the potential to produce earthquakes in the future similarly to those that were produced in the past, and that the most destructive earthquakes will likely occur on the southwest segments of the fault according to geomorphic indices.

Relationship between the regional tectonic activity and crustal structure in the eastern Tibetan plateau discovered by gravity anomaly

The eastern Tibetan plateau has been getting more and more attention because it combines active faults,uplifting, and large earthquakes together in a high-population region. Based on the previous researches, the most of Cenozoic tectonic activities were related to the regional structure of the local blocks within the crustal scale. Thus,a better understanding of the crustal structure of the regional tectonic blocks is an important topic for further study. In this paper, we combined the simple Bouguer gravity anomaly with the Moho depths from previous studies to investigate the crustal structure in this area. To highlight the crustal structures, the gravity anomaly caused by the Moho relief has been reduced by forward modeling calculations. A total horizontal derivative（THD） had been applied on the gravity residuals. The results indicated that the crustal gravity residual is compatible with the topography and the geological settings of the regional blocks,including the Sichuan basin, the Chuxiong basin, the Xiaojiang fault, and the Jinhe fault, as well as the Longmenshan fault zone. The THD emphasized the west margin of Yangtze block, i.e., the Longriba fault zone and the Xiaojiang fault cut through the Yangtze block. The checkboard pattern of the gravity residual in the SongpanGarze fold belt and Chuandian fragment shows that the crust is undergoing a southward and SE-directed extrusion,which is coincident with the flowing direction indicatedfrom the GPS measurements. By integrating the interpretations, the stepwise extensional mechanism of the eastern Tibetan plateau is supported by the southeastward crustal deformation, and the extrusion of Chuandian fragment is achieved by Xianshuihe fault.

Assessment of Recent Tectonic Activity along the Yamuna Basin, Garhwal Region, NW-Himalaya, India: Based on Morphotectonic Analysis

Decoupling between climate and tectonics, transform the elevation of earth surface regionally by denudation and displacement of land. To extract the tectonic footprints on morphology of landform, geormophometry is widely accepted tool due to visible responses in Drainage architecture to an intense tectonic environment. The present morphology of Yamuna basin in the Garhwal Himalaya, India is a result of continuing crustal deformation;erosion and deposition in the area. The drainage system and geomorphic expression of topography have been significantly influenced by active tectonics in this basin. In present study, for numerical modelling to detect the influence of tectonic signals on landform, we used morphotectonic parameters, to gradient index (SL), valley floor height to width ratio (Vf), asymmetry factor (Af), basin shape index (BS) and hypsometric integral (HI), extracted from SRTM DEM with resolution of 30 m. All these morphotectonic parameters are integrated to produce an index of relative active tectonics (IRAT). The Yamuna basin is classified into three groups based on IRAT, very high (<2.0);moderate (2.0 - 2.25) and low (>2.25) based on the degree of tectonic activity. Result shows approx. 56% of Yamuna basin experience high tectonic activity. This along strike deformation pattern pronouncedly emulates subsurface geometry based tectonic model.

Tectonic geomorphology of Türkiye and its insights into the neotectonic deformation of the Anatolian Plate

Quantitative geomorphic analyses are usually powerful in identifying active tectonics across global orogenic belts.Our present study will focus on the Anatolian Plate which hosts a lot of recent catastrophic earthquakes in Türkiye.Six geomorphic indices for 100 sub-basins around Türkiye have been computed including local relief,slope,normalized steepness index(k_(Sn)),hypsometric curve and integral(HI),transverse topographic symmetry factor(Tf),and the basin asymmetry factor(Af).The averaged kSnand Af values have shown four high-value anomalous zones,suggesting relatively high uplift rates featured by high river incision and regional tilting.The values of 0.35≤HI<0.6 for basins with S-shaped curves imply intensive tectonic activities along the eastern part of the North Anatolian Fault Zone(NAFZ),the Northeast Anatolian Fault Zone(NEAFZ),the East Anatolian Fault Zone(EAFZ),and the Central Anatolian Fault Zone(CAFZ).All results of the geomorphic indices analysis suggest a relatively high degree of tectonic activity in the following four areas,the Isparta Angle,the Eastern Black Sea Mountains,the South-eastern Anatolia Region,and the Central Anatolian fault zone.We further suggest that the eastern part of the NAFZ,NEAFZ,EAFZ,and CAFZ will be more active in tectonic activities,with a greater potential for strong earthquake occurrence.

Geomorphic signatures and active tectonics in western Saurashtra,Gujarat,India

Active tectonics in an area includes ongoing or recent geologic events.This paper investigates the tectonic influence on the subsidence,uplift and tilt of western Saurashtra through morphotectonic analysis of ten watersheds along with characteristics of relief and drainage orientation.Watersheds 7-9 to the north(N)are tectonically active,which can be linked with the North Kathiawar Fault System(NKFS)and followed by watersheds 6,10,1,4 and 5.Stream-length gradient index and sinuosity index indicate the effect of tectonic events along the master streams in watersheds 6-9.Higher R^(2)values of the linear curve fit for watershed 7 indicate its master stream is much more tectonically active than the others.The R^(2)curve fitting model and earthquake magnitude/depth analysis confirm the region to be active.The reactivation of the NKFS most likely led to the vertical movement of western Saurashtra.

A thermal physical index to explore current tectonic activity with satellite remote sensing

The use of satellite thermal infrared information is being developed as a method of exploring current tectonic activity. To realize real world application, an objective, stable and testable thermal physical index that is simultaneously related with tectonic activity must be established. From the viewpoint of the energy balance, the land surface is a boundary where energy is exchanged between outer space and the solid Earth. Regardless of how complex the influencing factors are, the land surface is mainly affected by the Sun, atmosphere and underground heat. In this paper, first, the relationships among land surface temperature, solar radiation, atmospheric temperature and thermal information from underground are obtained employing a mathematic physical method based on the equation of heat conduction and energy balance at the land surface. Second, a thermal physical index called the geothermal flux index (GFI), which can provide the activity state of underground heat, is constructed. Third, the theoretical basis of the thermal physical index is verified using stable annual variations in land surface temperature and solar radiation. Finally, combined with known crustal deformations derived using a global positioning system, the effectiveness of the GFI in extracting field tectonic motion is tested. The results indicate that the GFI is effective in providing information on current tectonic activity.

GIS-Based Analysis of Relative Tectonic Activity along the Kazerun Fault Zone, Zagros Mountains, Iran: Insights from Data Mining of Geomorphic Data

This paper tests a data mining method for evaluation of the ＂IRTA＂（Index of Relative Tectonic Activity） to investigate the impact of active tectonics on geomorphic processes and landscape development. Based upon K-means clustering of six basin-related geomorphic indices（the hypsometric integral, basin asymmetric factor, drainage density, basin shape ratio, mean axial slope of the channel and topographic roughness） that represent the relative strength of active tectonic deformation on topography and morphology, the relative tectonic activity along the Kazerun Fault Zone in the Zagros Mountains of Iran may be classified into low, moderate and high relative tectonic activity zones. The results allow the identification of the clusters of similarly deformed areas related to relative tectonic activity. The utilization of geomorphic parameters as well as IRTA with comparison to the field observations exhibit change in relative tectonic activities mostly corresponding to the change in mechanism of the prominent fault zones in the study area.

Research on the Characteristics of Large Earthquake Activity on the Active Tectonic Boundaries on the Chinese Mainland

Based on the research and the division of the active tectonic blocks and their boundaries on the Chinese mainland, the feature of the large earthquake activities on the 24 boundaries between the 6 active tectonic block regions (grade Ⅰ) and the 22 active tectonic blocks (grade Ⅱ) are studied. The seismicity levels on the active tectonic block boundaries are discussed considering the large earthquake frequency and the released strain energy in unit distance and time. The theoretic maximal magnitude and the recurrence period of each boundary are then calculated from the G-R relation. By comparing this with the actual earthquake records, it is found that the intensities of the earthquake deduced from the seismic activity parameter (a/b) on the main active boundaries on the Chinese mainland are consistent with that of the natural earthquakes. Meanwhile, an inverse relation is found between the recurrence periods of large earthquakes and the tectonic motion rate on the boundaries. These results show that the a, b values of each boundary obtained in this paper are valuable. In addition, the present seismic activities and hazards of these boundaries are also probed into with the historical data and their elapsed time on each boundary based on the hypothesis that the large earthquakes satisfy Poisson distribution.

The Deformation of Active Tectonic Blocks on the Chinese Mainland and Its Relationship with Seismic Activity

Based on the hypothesis of the active tectonic blocks on the Chinese continent and its adjacent regions (both the method of the DDA on a spherical surface and the GPS survey results observed from 1991 to 2001 are used), the movements and deformations of each active tectonic block are calculated. The calculation results show that although the movements and deformations of active tectonic blocks in the eastern region and in the western region of China are different, active tectonic blocks in the same active tectonic block region are coherent. Then, the relative velocities of the active tectonic blocks’ boundary zones are calculated, and the relationship between current crustal motion and strong seismic activities is discussed. Earthquakes ( M S≥7 0) on the Chinese continent since 1988 all occurred on boundary zones of active tectonic blocks with high slipping speed.

Late Quaternary fluvial terrace formation in the Luan River drainage basin,north China and its possible linkages with climate change and tectonic activation

The Luan River is the most important water system in north-eastern Hebei Province,China and is located in the transitional zone of the Eastern Yan Mountains,North China Plain and Songliao Plain.The well-developed river terraces of its tributary,the Yixun River,provide excellent information for studying neotectonics and climate change.There are seven terraces in the lower reaches of the Yixun River,numbered T7-T1.The optically stimulated luminescence dating results of 23 samples show that terraces T7-T2 formed at 111.36±5.83 ka,78.20±4.45 ka,65.29±4.15 ka,56.44±3.07 ka,40.08±2.66 ka,and 13.14±0.76 ka,respectively.A comparison with the oxygen isotope curves of deep-sea sediments reveals that the sediment formation of each terrace corresponded to cold periods of marine isotope stages MIS 4 and MIS 2 and the relatively cold periods of MIS 5e,MIS 3,and MIS 1.Since the Late Pleistocene,the incision rate of the Yixun River has ranged from 0.371-1.740 mm/a.During the formation of T7-T6,T5-T4,T4-T3,and T3-T2,the incision rate was low.However,in the two stages during which T6-T5 and T2-T1 formed(13.14±0.76 ka to 0.58±0.08 ka and 10.79±0.64 ka to 0.16±0.01 ka),these rates reached 1.554 mm/a and 1.592-1.740 mm/a,respectively.At approximately 30 ka,the activity of the Langying Fault increased,leading to footwall uplift.The river gathered in the north of Langying to form the ancient Erdaowan Lake,which resulted in the drying of the river in the lower reaches of the Yixun River during the last glacial maximum without forming river deposits.In the Early Holocene,headward erosion in the lower reaches of the Yixun River was enhanced,which resulted in the disappearance of the lake,and incised meandering formed due to increased neotectonism.Based on the analyses of river incision and the formation of ancient lakes and incised meandering,it was inferred that there have been three periods of strong tectonism in the river basin since the Late Pleistocene.

Relative active tectonic in the metamorphic rocks of the Yaounde group: insights from geomorphic indices and topographic analysis

The Yaounde Group(YG),representing the southern edge of the North Equatorial PanAfrican Belt,consists of quartzites,schists,micaschists,amphibolites,gneisses and migmatites.Tectonism has formed a landscape characterized by the development of linear and folded valleys and ridges,fault scarps,V-shaped valleys,incised rivers and knickpoints.These landforms constitute important markers of the regional tectonic activity,which have been computed from spatial sources such as SRTM,DEM,hydrographical networks and geomorphic indices such as AF,T,Smf,Vf,Bs,Hi,U,SI and Li.The results highlighted a mature relief consisting of asymmetric basins generated by tilting and uplift phenomena.The relative index of active tectonics(RIAT)has been estimated from an average of eight geomorphic indices evaluated on 24 subbasins,in the study area.Four classes have been defined:class 1(1.38),very high active(1.0≤RIAT<1.5);class 2(1.50-1.88),high active(1.5≤RIAT<2.0);and class 3(2.00-2.13)moderate active(2.0≤RIAT<2.5).These three classes,respectively covering 10.20%(458 km2),80.10%(3595 km2)and 9.69%(435 km2)of the study area,have shown a highly active tectonic zone,and imply the existence of a neotectonic event in the YG.This tectonic unit(YG)was also affected by the dextral NW-SE strike-slip faulting,which cross-cut the Sanaga Shear Zone(SSZ)at Ebebda and the foliation oriented NW-SE.The tilting and uplift of rocks related to Moho ascending are responsible for crustal thinning in the Cameroon basement,more important to the Adamawa Plateau from the Cretaceous age and the reactivation of existing tectonic accidents.The presence of hills,fault scarps,reverse faults,knickpoints,V and U shaped valleys and rounded mountains testify to the interaction between tectonic uplift,lithology,climate,weathering and erosion.

ON TECTONIC PROBLEMS OF THE OKINAWA TROUGH

The Okinawa Trough is a very active tectonic zone at the margin of the Northwest Pacific and is typical of back arc rifting at the young stage of tectonic evolution. Many scientists from Japan, China, Germany, France, the U.S.A. and Russia have done a lot of geologic and geophysical investigations there. It is well known that the Okinawa Trough is an active back arc rift with extremely high heat flow, very strong hydrothermal circulation, strong volcanic and magmatic activity, frequent earthquakes, rapid subsidence and rifting, well developed fault and central graben. But up to now, there are still some important tectonic problems about the Okinawa Trough that require clarification on some aspects such as the type of its crust, its forming time, its tectonic evolution, the distribution of its central grabens, the relationship between its high heat flow and tectonic activity. Based on the data obtained from seismic survey, geomagnetic and gravity measurements, submarine sampling and heat flow measurements in the last 15 years, the author discusses the following tectonic problems about the Okinawa Trough: (1) If the Okinawa Trough develops oceanic crust or not. (2) Is the South Okinawa Trough tectonically more active than the North Okinawa Trough with shallower water and few investigation data on it. (3) The formation time of the Okinawa Trough and its tectonic evolution. The Okinawa Trough has a very thin continental crust. Up to now, there is no evidence of oceanic crust in the Okinawa Trough. The North, Middle and South Okinawa Trough are all very strongly active areas. From 6 Ma B.P., the Okinawa Trough began to form. Since 2 Ma, the Okinawa Trough has been very active.

Satellite Data-based Structural Mapping Reveals Active Panjal Traps Fault(PTF)in Kashmir,NW Himalaya

Exploring the evidence for unidentified earthquake-causing faults in the orogenic zones,and primarily the interior parts(Shah,2013),has been an ongoing quest for centuries(Willis,1923;Baker et al.,1988;Yeats et al.,1992;Wesnousky et al.,1999;Malik et al.,2010;Coudurier-Curveur et al.,2020;Shah et al.,2020).These faults are potentially dangerous due to their unknown risk and deformation budget,two of the most important aspects of mapping and understanding the vulnerability and hazards associated with active faults.

Tectonic control on slow-moving Andean landslides in the Colca Valley,Peru

The Colca Valley in the Central Andes is a region characterized by the occurrence of large slow-moving landslides and a high level of seismic activity.In this study,we aimed to determine passive and active tectonic control on the formation of selected five large landslides in the Colca Valley and to assess geohazard associated with these features.For that purpose,we performed a post-landslide field survey,applied remote sensing techniques,and obtained eyewitness accounts.Recently,the need to understand mass movement processes in this region is even higher due to the establishment of the Colca y Volcanes de Andagua Geopark(Colca and Andagua Volcanoes Geopark).Our results suggest that the studied landslides usually represent a complex failure mechanism,dominated by translational sliding or rotational displacements,commonly associated with the formation of horst-and-graben like structures.We found a spatial correlation between the distribution of landslides and inherited fault network.The head scarps appear to be limited by the WNW-to NW-striking faults,whereas the lateral extent of some of the reported features seems to be connected with the NNE-striking normal faults,common in both,the Mesozoic strata and the Pleistocene-Holocene deposits.

Characteristics of helium isotopes in natural gas and its tectonic implication in Bohai Bay Basin

Analysis on helium isotopes in natural gas in Bohai Bay Basin showed their mantle-origin indicated by high 3He/4He ratio. The span of 3He/4He ratio increased from west to east. This pattern im- plied a close relationship to the local tectonic setting. Bohai Bay Basin experienced intensive neo-tectonic activities in the Cenozoic. Widespread faulted-depressions and strong volcanic eruptions manifested its extensional tectonics. Abiogenic natural gas could be released from magmas and migrate upward through deep faults during the extension. Tectonic conditions in the area would favor upward invasion and reser- vation of mantle-originated helium. Furthermore, with decrease of convergence rate between the Pacific and the Eurasia Plate, the subduction slab of the Pacific Plate rolled back and became steeper, resulting in mantle flow and other tectonic activities migrating from west to east in nature, and caused the variation in isotopic helium ratios.

Geological Structure and Quaternary Activity of the Zhangjiakou Fault, Northern China

Based on detailed field investigations, this paper describes the geometrical characteristics and tectonic activities of the Zhangjiakou fault at the northwest of Beijing. This fault strikes mainly northwest to west, short parts of which strike near east to west, dipping north, and extends over a length of 70km. It is a major geological and geomorphologicai margin, controlling the neotectonic movement in this region. On the south side of the Zhangjiakou fault are the Late Quaternary unconsolidated deposits, forming basins; while on the other side are Mesozoic volcano debris and Pre-Mesozoic metamorphic rocks, forming lower mountains and hills. The Zhangjiakou fault consists mainly of high-angle inverse strike-slip fault and partially of normal strike-slip fault. Among these, the north-dipping NW-NWW-trending secondary faults, constituting the main fracture of the fault, have inverse characteristics; those near the EW-trending secondary faults are links of the former faults, with a smaller length and normal faulting characteristics. Thus, the Zhangjiakou fault is a north-dipping inverse and partially south-dipping normal strike-slip fault. The Zhangjiakou fault has been continuously active since the Quaternary. With the exception of the western end extension, which has been active since the late Pleistocene, the main part of the fault has been active since the Holocene. The central main segment of the Zhangjiakou fault is more active. Since the mid-late period of the late Pleistocene, the average vertical slip rate of a single fault has been over 0. 07mm/a - 0. 30mm/a. The Zhangjiakou fault has multi-slip surfaces, and the total vertical slip rate reaches 1.33mm/a, estimated from the Qingshuihe river terraces and the relevant drilling data.

Active Faulting Pattern,Present-day Tectonic Stress Field and Block Kinematics in the East Tibetan Plateau

This paper examines major active faults and the present-day tectonic stress field in the East Tibetan Plateau by integrating available data from published literature and proposes a block kinematics model of the region. It shows that the East Tibetan Plateau is dominated by strike-slip and reverse faulting stress regimes and that the maximum horizontal stress is roughly consistent with the contemporary velocity field, except for the west Qinling range where it parallels the striking of the major strike-slip faults. Active tectonics in the East Tibetan Plateau is characterized by three faulting systems. The left-slip Kunlun-Qinling faulting system combines the east Kunlun fault zone, sinistral oblique reverse faults along the Minshan range and two major NEE-striking faults cutting the west Qinling range, which accommodates eastward motion, at 10--14 mm/a, of the Chuan-Qing block. The left-slip Xianshuihe faulting system accommodated clockwise rotation of the Chuan-Dian block. The Longmenshan thrust faulting system forms the eastern margin of the East Tibetan Plateau and has been propagated to the SW of the Sichuan basin. Crustal shortening across the Longmenshan range seems low （2-4 mm/a） and absorbed only a small part of the eastward motion of the Chuan-Qing block. Most of this eastward motion has been transmitted to South China, which is moving SEE-ward at 7-9 mm/a. It is suggested from geophysical data interpretation that the crust and lithosphere of the East Tibetan Plateau is considerably thickened and theologically layered. The upper crust seems to be decoupled from the lower crust through a decollement zone at a depth of 15-20 kin, which involved the Longmenshan fault belt and propagated eastward to the SW of the Sichuan basin. The Wenchuan earthquake was just formed at the bifurcated point of this decollement system. A rheological boundary should exist beneath the Longmenshan fault belt where the lower crust of the East Tibetan Plateau and the lithospheric mantle of the Yangze block are juxtaposed.

Uniform Strike-Slip Rate along the Xianshuihe-Xiaojiang Fault System and Its Implications for Active Tectonics in Southeastern Tibet

Recent studies on the Xianshuihe-Xiaojiang fault system suggest that the Late Quaternary strike-slip rate is approximately uniform along the entire length of the fault zone, about 15±2 mm/a. This approximately uniform strike slip rate strongly supports the clockwise rotation model of the southeastern Tibetan crust. By approximating the geometry of the arc-shaped Xianshuihe-Xiaojiang fault system as a portion of a small circle on a spherical Earth, the 15±2 mm/a strike slip rate corresponds to clockwise rotation of the Southeastern Tibetan Block at the （5.2±0.7）×10^-7 deg/a angular velocity around the pole （21°N, 88°E） relative to the Northeast Tibetan Block. The approximately uniform strike slip rate along the Xianshuihe-Xiaojiang fault system also implies that the Longmeushan thrust zone is not active, or at least its activity has been very weak since the Late Quaternary. Moreover, the total offset along the Xiaushuihe-Xiaojiang fault system suggests that the lateral extrusion of the Southeastern Tibetan Block relative to Northeastern Tibetan Block is about 160 km and 200-240 km relative to the Tarim-North China block. This amount of lateral extrusion of the Tibetan crust should have accommodated about 13-24% convergence between India and Eurasia based on mass balance calculations. Assuming that the slip rate of 15±2 mm/a is constant throughout the entire history of the Xianshuihe-Xiaojiang fault system, 11±1.5 Ma is needed for the Xianshuihe-Xiaojiang fault system to attain the 160 km of total offset. This implies that left-slip faulting on the Xianshuihe-Xiaojiang fault system might start at 11±1.5 Ma.

Relative active tectonics evaluation using geomorphic and drainage indices, in Dadra and Nagar Haveli, western India

The present study area,Dadra and Nagar Haveli,contains several lineaments and traces of active faults.The various aspect of the geomo rphic analysis,i.e.,stream length(SL) gradient,hypsometric integral(HI),basin shape(BS),valley floor(VF),have been applied to evaluate the relative index of active tectonics(RIAT) of the Damanganga watershed.The high and low zones of tectonic activity have been identified based on the geomorphic analysis of the watershed.After evaluation of all indices,three classes,class IIhigh(1.3 ≤RIAT <1.5),class Ⅲ-moderate(1.5 ≤RIAT <1.8),and class Ⅳ-low(1.8 ≤RIAT),have been obtained to outline the degree/gradation of comparative tectonic activities in the study area.The appraised outcome of the RIAT dispersal is also well reinforced by the geomorphic evidence in the field.The collective outcomes of geomorphic evidence,such as stream deflection and analysis of lineament,deflection of streams,and geomorphic indices,conceal that the Damanganga watershed is affected by tectonic activity.