This paper focuses on the in-depth analysis of the aeromagnetic characteristics of the Dunhua-Mishan fault zone and its surrounding areas using wavelet multi-scale analysis. In order to analyze the anomalies of the crustal structure at different depths, wavelet multi-scale decomposition is used to separate the deep field from the shallow field sources, superimpose the aeromagnetic anomalies on different anomalies of different geological bodies, extract the required information, analyze the local field anomalies caused by the field sources, and invert and interpret the geological bodies. In this paper, wavelet multi-scale analysis is used to decompose the aeromagnetic data, separate the deep and shallow field sources of aeromagnetism in the study area, and obtain wavelet detail maps of order 1 to 4. The wavelet transform detail maps are a response to high frequency anomaly information, and also a reflection of local field aeromagnetic anomaly information, which can be used to infer information such as fault depth and basement depth of basin. The experimental results are used to analyze the anomaly characteristics at different depths, invert and analyze the characteristics of the aeromagnetic anomalies and crustal structure at different depths, explore the deep basement and fault tectonic features and the intersection relationship between the Dunhua-Mishan Fault and the surrounding faults, calculate the approximate field source depth by wavelet detail map and power spectrum method, and infer the fault cut-through depth. The results of the analysis can provide geophysical research information for the study of geotectonics and the evaluation and exploration of hydrocarbon resources.
Based on the original aeromagnetic anomaly map, aeromagnetic anomalies ranging from -494~2022nT can be obtained, with the highest anomaly located at about 50km from Baoqing County. The anomalies in the central part of the study area are high, while those in the eastern and western parts are low. The deposition of basal and ultramafic magmatic rocks in the Dunhua-Mishan area has caused massive high anomalies, while deep and large faults caused basement uplift or decline, shown as high and low anomaly zones. In the aeromagnetic shallow source field, the shallow surface and upper crustal media are more complex, and the Dunhua-Mishan fault zone shows multi-pearl-like small-scale anomalies, resulting mainly from the intrusion of basal or ultramafic magmatic rocks in the shallow part of the fault. In the deep source field, the magnetic anomalies in middle and lower crust are mainly caused by different magnetic properties of basin bedrock. The large fault zone presents as the dividing line of different trajectory feature zones, and the deep large fault cuts deeper and presents as the dividing line of different trajectory feature zones. The cut-through depth of the deep major faults is larger and affects the aeromagnetic characteristics of the deep tectonic zone. The paper further discusses the cut-through depth of the major faults of this region by analyzing the characteristics of the aeromagnetic anomalies at different depths and finds that there are the three deep major faults in the region, namely, the Dunhua-Mishan Fault, the Dahezhen Fault and the Yilan-Yitong Fault, while the Hulin River Fault, the Muling River Fault, the Fujin-Xiaojia River Fault and the Nanbeihe-Boli Fault only cut through the shallow crust; the Muling River Fault, the Dunhua-Mishan Fault, the Dahezhen Fault and the Fujin-Xiaojia River Fault only intersect in the shallow crust. The Parker method was used to invert the depth of the Curie points in the area, and the results show that the depth of the Curie points in the area ranges from 22.3~29.9km, with the deepest area in the south of Hulin County, which is a depressional basin formed by plate subduction and extrusion, and the Dunhua-Mishan fault zone has a controlling effect on the morphology of the Curie points. Seismic activity is low in the region as a whole, and earthquakes are densely distributed in the northwest of the study area along the Yilan-Yitong fault zone, and less distributed along the Dunhua-Mishan fault zone and the Dahezhen fault zone. In the vicinity of the Dunhua-Mishan fault zone, small earthquakes are mainly concentrated in the area south of the Mishan sub-uplift, and the northern section of the Dunhua-Mishan fault zone is generally more stable. The gravity field in this area has been studied in depth by previous authors. The area belongs to the Moho surface uplift zone in Heilongjiang Province, with the Moho depth of about 30~32.5km. The Yilan-Yitong rift zone is deep to the Moho surface, and the Moho surface often shows uplift in the seismically active area. The local deformation and uplift of the crust-mantle provides the possibility of stress concentration, while the existence of deep major faults provides a channel for material transport. The overall level of seismic activity in the region is low, and the areas with intense activity are mainly concentrated in the Yilan-Yitong fault zone, with small earthquakes also gathering near the Jixi area. Seismicity of Qitaihe-Jixi area is mainly influenced by the Mudanjiang Fault and the Nanbei River Fault. The Dunhua-Mishan Fault has a strong influence on the distribution of Curie points and also influences the formation of several major tectonic units. So, more attention should be paid to the crustal activity of areas around the faults and at the intersections of faults in the future.

The current and conventional fault-crossing short baseline measurement has a relatively high precision, but its measurement arrays usually fail to or cannot completely span major active fault zones due to the short length of the baselines, which are only tens to 100 meters. GNSS measurement has relatively low resolution on near-fault deformation and hence is not suitable for monitoring those faults with low motion and deformation rates, due to sparse stations and relatively low accuracy of the GNSS observation. We recently built up two experimental sites on the eastern boundary of the active Sichuan-Yunnan block, one crossing the Daqing section of the Zemuhe Fault and the other crossing the Longshu section of the Zhaotong Fault, aiming to test the measurement of near-fault motion and deformation by using fault-crossing arrays of one-kilometer-long baselines. In this paper, from a three-year-long data set we firstly introduce the selection of the sites and the methods of the measurement. We then calculate and analyze the near-field displacement and strain of the two sites by using three hypothetical models, the rigid body, elastic and composed models, proposed by previous researchers. In the rigid body model, we assume that an observed fault is located between two rigid blocks and the observed variances in baseline lengths result from the relative motion of the blocks. In the elastic model, we assume that a fault deforms uniformly within the fault zone over which a baseline array spans, and in the array baselines in different directions may play roles as strainmeters whose observations allow us to calculate three components of near-fault horizontal strain. In the composed model, we assume that both displacement and strain are accumulated within the fault zone that a baseline array spans, and both contribute to the observed variances in baseline lengths. Our results show that, from the rigid body model, variations in horizontal fault-parallel displacement component of the Zemuhe Fault at the Daqing site fluctuate within 3mm without obvious tendencies. The displacement variation in the fault-normal component keeps dropping in 2015 and 2016 with a cumulative decrease of 6mm, reflecting transverse horizontal compression, and it turns to rise slightly(suggesting extension)in 2017. From the elastic model, the variation in horizontal fault-normal strain component of the fault at Daqing shows mainly compression, with an annual variation close to 10^-5, and variations in the other two strain components are at the order of 10^-6. For the Longshu Fault, the rigid-body displacement of the fault varies totally within a few millimeters, but shows a dextral strike-slip tendency that is consistent with the fault motion known from geological investigation, and the observed dextral-slip rate is about 0.7mm/a on average. The fault-parallel strain component of the Longshu Fault is compressional within 2×10^-6, and the fault-normal strain component is mainly extensional. Restricted by the assumption of rigid-body model, we have to ignore homolateral deformation on either side of an observed fault and attribute such deformation to the fault displacement, resulting in an upper limit estimate of the fault displacement. The elastic model emphasizes more the deformation on an observed fault zone and may give us information about localizations of near-fault strain. The results of the two sites from the composed model suggest that it needs caution when using this model due to that big uncertainty would be introduced in solving relevant equations. Level surveying has also been carried out at the meantime at the two sites. The leveling series of the Daqing site fluctuates within 4mm and shows no tendency, meaning little vertical component of fault motion has been observed at this site; while, from the rigid-body model, the fault-normal motion shows transverse-horizontal compression of up to 6mm, indicating that the motion of the Zemuhe Fault at Daqing is dominantly horizontal. The leveling series of the Longshu site shows a variation with amplitude comparable with that observed from the baseline series here, suggesting a minor component of thrust faulting; while the baseline series of the same site do not present tendencies of fault-normal displacement. Since the steep-dip faults at the two sites are dominantly strike-slip in geological time scale, we ignore probable vertical movement temporarily. In addition, lengths of homolateral baselines on either side of the faults change somewhat over time, and this makes us consider the existence of minor faults on either side of the main faults. These probable minor faults may not reach to the surface and have not been identified through geological mapping; they might result in the observed variances in lengths of homolateral baselines, fortunately such variations are small relative to those in fault-crossing baselines. In summary, the fault-crossing measurement using arrays with one-kilometer-long baselines provides us information about near-fault movement and strain, and has a slightly higher resolution relative to current GNSS observation at similar time and space scales, and therefore this geodetic technology will be used until GNSS networks with dense near-fault stations are available in the future.

The northern margin of the Qinghai-Tibet Plateau is currently the leading edge of uplift and expansion of the plateau. Over the years, a lot of research has been carried out on the deformation and evolution of the northeastern margin of the Qinghai-Tibet Plateau, and many ideas have been put forward, but there are also many disputes. The Altyn Tagh Fault constitutes the northern boundary of the Qinghai-Tibet Plateau, and there are two active faults on the north side of the Altyn Tagh Fault, named Sanweishan Fault with NEE strike and Nanjieshan Fault with EW strike. Especially, studies on the geometric and kinematic parameters of Sanweishan Fault since the Late Quaternary, which is nearly parallel with the Altyn Tagn Fault, are of great significance for understanding the deformation transfer and distribution in the northwestward extension of the Qinghai-Tibet Plateau. Therefore, interpretation of the fault landforms and statistical analysis of the horizontal displacement on the Sanweishan Fault and its newly discovered western extension are carried out in this paper. We believe that the Sanweishan Fault is an important branch of the eastern section of the Altyn Tagh fault zone. It is located at the front edge of the northwestern Qinghai-Tibet Plateau and is a left-lateral strike-slip and thrust active fault. Based on the interpretation of satellite imagery and microgeomorphology field investigation of Sanweishan main fault and its western segments, it's been found that the Sanweishan main fault constitutes the contact boundary between the Sanweishan Mountain and the alluvial fans. In the bedrock interior and on the north side of the Mogao Grottoes, there are also some branch faults distributed nearly parallel to the main fault. The main fault is about 150km long, striking 65°, mainly dipping SE with dip angles from 50° to 70°. The main fault can be divided into three segments in the spatial geometric distribution:the western segment(Xizhuigou-Dongshuigou, I), which is about 35km long, the middle segment(Dongshuigou-Shigongkouzi, Ⅱ), about 65km long, and the east segment(Shigongkouzi-Shuangta, Ⅲ), about 50km long. The above three segments are arranged in the left or right stepovers.
In the west of Mingshashan, it's been found that the fault scarps are distributed near Danghe Reservoir and Yangguan Town in the west of Minshashan Mountain, and we thought those scarps are the westward extension of the main Sanweishan Fault. Along the main fault and its western extension, the different levels of water system(including gullies and rills)and ridges have been offset synchronously, forming a series of fault micro-geomorphology. The scale of the offset water system is proportional to the horizontal displacement. The frequency statistical analysis of the horizontal displacement shows that the displacement has obvious grouping characteristics, which are divided into 6 groups, and the corresponding peaks are 3.4m, 6.7m, 11.4m, 15m, 22m and 26m, respectively. Among them, 3.4m represents the coseismic displacement of the latest ancient earthquake event, and the larger displacement peak represents the accumulation of coseismic displacements of multi-paleoearthquake events. This kind of displacement characterized by approximately equal interval increase indicates that the Sanweishan Fault has experienced multiple characteristic earthquakes since the Late Quaternary and has the possibility of occurrence of earthquakes greater than magnitude 7. The distribution of displacement and structural transformation of the end of the fault indicate that Sanweishan Fault is an "Altyn Tagh Fault"in its infancy. The activities of Sanweishan Fault and its accompanying mountain uplift are the result of the transpression of the northern margin of the Qinghai-Tibet Plateau, representing one of the growth patterns of the northern margin of the plateau.

On January 21 2016, an earthquake of M_S6.4 hit the Lenglongling fault zone(LLLFZ)in the NE Tibetan plateau, which has a contrary focal mechanism solution to the Ms 6.4 earthquake occurring in 1986. Fault behaviors of both earthquakes in 1986 and 2016 are also quite different from the left-lateral strike-slip pattern of the Lenglongling fault zone. In order to find out the seismogenic structure of both earthquakes and figure out relationships among the two earthquakes and the LLLFZ, InSAR co-seismic deformation map is constructed by Sentinel -1A data. Moreover, the geological map, remote sensing images, relocation of aftershocks and GPS data are also combined in the research. The InSAR results indicate that the co-seismic deformation fields are distributed on both sides of the branch fault(F₂)on the northwest of the Lenglongling main fault(F₁), where the Earth's surface uplifts like a tent during the 2016 earthquake. The 2016 and 1986 earthquakes occurred on the eastern and western bending segments of the F₂ respectively, where the two parts of the F₂ bend gradually and finally join with the F₁. The intersections between the F₁ and F₂ compose the right-order and left-order alignments in the planar geometry, which lead to the restraining bend and releasing bend because of the left-lateral strike-slip movement, respectively. Therefore, the thrust and normal faults are formed in the two bending positions. In consequence, the focal mechanism solutions of the 2016 and 1986 earthquakes mainly present the compression and tensional behaviors, respectively, both of which also behave as slight strike-slip motion. All results indicate that seismic activity and tectonic deformation of the LLLFZ play important parts in the Qilian-Haiyuan tectonic zone, as well as in the NE Tibetan plateau. The complicated tectonic deformation of NE Tibetan plateau results from the collisions from three different directions between the north Eurasian plate, the east Pacific plate and the southwest Indian plate. The intensive tectonic movement leads to a series of left-lateral strike-slip faults in this region and the tectonic deformation direction rotates clockwise gradually to the east along the Qilian-Haiyuan tectonic zone. The Menyuan earthquake makes it very important to reevaluate the earthquake risk of this region.

To research the faults distribution and deep structures in the southern segment of Tan-Lu fault zone(TLFZ) and its adjacent area, this paper collects the Bouguer gravity data and makes separation by the multi-scale wavelet analysis method to analyze the crustal transverse structure of different depths. Meanwhile Moho interface is inversed by Parker variable density model. Research indicates that the southern segment of TLFZ behaves as a NNE-directed large-scale regional field gravity gradient zone, which separates the west North China-Dabie orogen block and the east Yangtze block, cutting the whole crust and lithosphere mantle. There are quite differences of density structures and tectonic features between both sides of this gradient belt. The sedimentary and upper crustal density structure is complex. The two east branches of TLFZ behave as linear gravity anomalous belt throughout the region, whereas the two west branches of TLFZ continue to extend after truncating the EW-trending gravity anomaly body. The lower crustal density structure is relatively simple. TLFZ behaves as a broad and gentle low abnormal belt, which reflects the Cretaceous-Paleogene extension environment caused graben structure. The two west branches of TLFZ, running through Hefei city, extend southward along the west margin of Feidong depression and pinch out in Shucheng area due to the high density trap occlusions in the south of Shucheng. The Feizhong Fault, Liu'an-Hefei Fault, and Feixi-Hanbaidu Fault intersect the two west branch faults of TLFZ without extending to the east. Recent epicenters are mainly located in conversion zones between the high-density and the low-density anomaly, especially in TLFZ and the junction of the faults, where earthquakes frequently occurred in the upper and middle crust. As strong earthquakes rarely occur in the southern segment of TLFZ, considering its deep feature of abrupt change of the Moho and intersections with many EW-trending faults, the hazard of strong earthquake cannot be ignored.

Yishu Fault zone is the Shandong segment of Tan-Lu Fault zone, which is characterized by remarkable neotectonic activities and is one of the strong earthquake activity belts in North China. Wavelet multi-scale analysis method is applied to separate gravity fields effectively to study the features of crust structures and spatial distribution of faults with collected Bouguer gravity data of this area. Moho depths are inversed by using the variable density model. The following conclusions are concluded: (1)The gravity fields show that the Yishu Fault zone forms a large-scale NNE-striking gravity gradient zone, which separates the western Shandong block and eastern Shandong block as a major geophysical boundary in this area. (2)The local gravity fields show that the structure of mid and upper crust is complex. The gravity anomaly pattern of 1 horst trapped between 2 grabens appears in the Yishu Fault zone and 5 main faults distributed in the east and west grabens form a linear gradient zone. Many NW-striking active faults in Western Shandong block intersect with Yishu Fault zone in the deep part. The majority of these faults intersect to the west graben of Yishu Fault zone. Only Mengshan Fault and Cangni Fault traverse the Yishu Fault zone. The structure of lower crust is relative simple, fold structures are evident, and there is typical characteristics of large-scale high and low density anomalies alternating in the lower crust.(3)In the Moho depths image, the east part is high and the west is low. The Yishu Fault zone forms the Moho abrupt change zone, creating the separating pattern. Uplift of Moho occurs along the east Weifang-Juxian-Linyi regions, providing deep conditions for strong earthquake preparation.(4)Earthquake epicenters are mainly located in conversion zones between the high and the low-density anomaly, especially in the transitional area from the low-density to high-density anomaly. The occurrence of earthquake is closely related to activity of fault. The Yishu Fault zone sees the strongest seismic activity in this area, and the seismicity in east graben is higher than that in west graben.

Based on ALOS, ETM+images and field works, combining with the existing research results of the study area, using information enhancement and image fusion methods, we extracted the texture, color and water-bearing features and studied the spatial distribution and development of the southeastern piedmont faults of the Nyenchen Tonglha Mountains. Moreover, SL index and Hack profile were used to analyze and compare the regional tectonic activity. The results show that the main faults obviously present a three-stage distribution on remote sensing images. Fault movement has produced different surface topography, such as fault scarp, fault facet and surface rupture zone. Small pull-apart basin, rift lakes and swamps were found in the basin. Their distribution and development are obviously controlled by faults. Geomorphic evidences interpreted from images generally indicate the fault movement property as normal faulting with strike-slip component. Major rivers cross the southeastern piedmont faults of the Nyenchen Tonglha Mountains from northwest to southeast and flow into Dangxiong-Yangbajain rift basins. The rivers with length bigger than four kilometers are selected to calculate the tectonic geomorphology parameters. The Hack profiles of rivers present obvious convex uplift that represents strong tectonic differential uplifting. Rivers had no time to make adjustments in the process of development and the tectonic movement produced convex and concave shape on the river section traces. The area where standard stream length-gradient index is abnormal indicates strong tectonic movement. This abnormal changes not only verify the impact on river profile caused by fault movement, but also improve the fault location accuracy when interpreted combining with these abnormal features. The average SL/K value in this area tends to increase from F₁ to F₃. From the point of historical earthquakes distribution, a large amount of small earthquakes occurred mainly on F₃ and seldom on F₁ and F₂. This trend is similar to SL/K value change. It indicates that the fault activity increases accordingly from F₁ to F₃. The standard length-gradient index K represents the river erosion ability, which increases from F₁ to F₃. This feature shows that normal fault movement is strong on F₃ and tectonic uplift has a significant impact on river erosion. Movement on F₁ and F₂ show strong strike-slip and weak normal faulting, whereas normal faulting is stronger on F₃. Dislocation of rivers is more evident on the remote sensing image. The southeastern piedmont faults of Nyenchen Tonglha Mountains and Dangxiong-Yangbajain rift basins are important conversion and absorption zones in the central Tibetan plateau, where the seismic activity is still high and more attention should be paid.

The activity of fault is one of the causes of earthquakes.The distribution of the velocity structure of small earthquakes on the fault structure can offer an accurate underground crust structure model for us to analyze the activity of fault.Using the seismic network monitoring data at the southern end of the Taihang Mountains and the small earthquake P wave travel time data,the paper reconstructs the three-dimensional velocity structure model for the southern end of the Taihang Mountains Fault zone by joint inversion of seismic source and velocity structure.The results show: on the west of Taihang Mountain piedmont fault zone,there exists a NNE-trending fault.Horizontal distribution shows a zonal distribution of low velocity zone along the fault zone.The thickness of the sedimentary layer in Taihangshan uplift has reduced gradually from approximately 8km to about 2km,while under the force from the western side,the crust thickens gradually.

Based on the remote sensing images interpretation,the spatial distribution of the Fei Huanghe(the ancient Yellow River)fault zone in Xuzhou area was studied and the intersection relationships between Fei Huanghe Fault and Shaolou Fault,and Tan-lu Fault were discussed in the paper.Besides,we researched the deep-seated geometric structure of Fei Huanghe Fault by studying the gravity-magnetic data,and discussed the intersection relationships with the west boundary of Tan-lu Fault. The cutting depth of Fei Huanghe Fault reflected by second order-wavelet transform detail of the Bouguer gravity anomalies is up to 7～8km.The depth reflected by the third order-wavelet and fourth order-wavelet transform detail of the Bouguer gravity anomalies is up to 9～11km and 15～18km,respectively.The results show that the Fei Huanghe Fault extends to Jiuding in southeast direction.The cutting depth is up to 8～9km.The NW-trending Fei Huanghe Fault cut the NE-trending Shaolou Fault,resulting in the change of the tectonic line of the latter from striking N 60°E to N 45°E.Moreover,the Fei Huanghe Fault didn't cut the Tanlu Fault.It is a pre-Quaternary Fault with weak activity.

The occurrence of earthquake is related to active structure,so the active structure is key to seismogeological study.For the broad field of vision of RS technology,it can play an important role in macro-active structure study.Furthermore,the ability of multi-temporal,multi-spectral,high-resolution,dynamic monitoring and so on also makes RS a very important tool for geological application.The studies of active fault using RS image were based on optical image before,therefore the study depends considerably on the fieldwork because of the limited information available from image.In the paper,we combine optical image with SAR image and implement image fusion,as a result,we can obtain more information and interpret more features of active fault.The paper puts emphasis on the study of distribution of active fault in Hainan Island utilizing satellite image.First,MSS,TM and SAR images are selected as the basis datum;preprocessing and image enhancements are manipulated for data fusion to highlight more features of geological body and extract more texture,tonal and other structure features to improve the efficiency of RS image greatly.Then the expression of geological physiognomy is analyzed,the symbol for interpretation is established,and each geological body on image is analyzed.At last,the geologic and geomorphic feature of the study area is analyzed generally,and detailed description of development of active fault in the northern area of Hainan Island is presented.After image processing and interpretation,we can conclude that there are mainly three groups of active faults striking EW,NW and NE,respectively in Qiongbei area.The EW-and NW-trending faults have great effect on the geologic and geomorphic development of the region.The image feature of active fault is clear,the phenomena of crustal movement such as linear distributed lake,volcano crater and flexed coastline,exist on the earth surface or near surface.The three groups of faults intersect with each other and have different movement intensities,which make the crust of the study area bitty and the physiognomic feature various.The movement of EW-and NW-trending faults is strong in this area.Along the NW-trending faults between Wangwu-Wenjiao and Puqian-Qinglan faults,the crustal deformation is intense in the Neoid period.Analysis indicates that the EW-and NW-trending active faults are highly active since the Quaternary,which affect significantly the stability of crust of the northern Hainan Island.

Dating the age of faulting is critical to the studies of active tectonics, paleoearthquake and neotectonics, but is sometimes difficult of access. At present, two methods are commonly used to date the age of the last faulting. The one is to date the direct products of faulting, such as fault gouge and colluvial wedge, while the other is to date the youngest sediment that was offset by faulting or the oldest sediment that was not affected by faulting. In the region from Tuoli to Yongdinghe River, western Beijing, three types of faulting can be identified along the Gaoliying fault. The first type is that the fault displaces the older loess layer, but is covered by the younger loess layer, such as the cases at Lujing and Xiaoyouying. The second type is observed at Xinkaikou, where the fault offsets the pre-Quaternary bedrocks, but does not affect the Quaternary covering layer (loess). The third type is identified at Xinzhuang village, where the fault dissects the pre-Quaternary bedrocks, resulting in fault gouge, but no Quaternary sediment covering the faults. According to the types of faulting and the characteristics of sediments, two dating methods were used to date the ages of faulting events on the Gaoliying fault in the region from Tuoli to Yongdinghe River, Beijing. Thermoluminescence dating method is suitable to dating eolian deposits, such as loess, and thus is used to date the loess samples affected by faulting or deposited after faulting. Electron Spin Resonance (ESR) dating method is currently the most reliable method to date fault gouge, and thus is used to date the ages of fault gouges collected from Xinzhuang and Dayuanshang villages, respectively. Based on the ages of faulting, it is coucluded that at least 3 faulting events had occurred on the Gaoliying fault at 270～360ka B.P., 130～140ka B.P and 1.8～4.2ka B.P, respectively.

In this paper,the techniques and applications of SAR interferometry are introduced. After a brief historical review,geometric implementations and important processing techniques of SAR interferometry are described. Besides,this paper illustrates technical flowchart for the spaceborne INSAR processing chain and recommends the measurement of coeismic displacements Landers earthquake by means of INSAR. This paper shows INSAR possess a good application perspective in extracting three dimensional information of the Earth’s surface.

Fault movements tend to result in the variation of landscape and water system regime, which can be displayed directly or indirectly on TM images through color and spatial texture features. Data image processing techniques were used to extract and analyze the water system features,texture features and the water-bearing information of Xianshuihe region. Detailed study was made on the geometric morphological features and tectonic geological background of Xianshuihe active fault zone.

Geological evidence indicates that the fault activity on the middle segment (Dali and its adjacent region) is the strongest along the Honghe fault (the Red River Fault).The active fault shows a distinct tendency of getting younger from the ends to the middle segment of the fault,i.e,faulting in the Dali area is the youngest,which coincides with the distribution of recent strong shocks.Geological evidence and its ages show that five events with a recurrence interval 昽f about 1500 years occurred in the middle-late Holocene time,presumably associated with an earthquake of M=8.

Displacement rale along the Honghe River fault (northern segment) since Pleistocene was determined in this paper on the basis of geological investigation:for the narrow valley segment (Dingxiling),offset rate is 8mm/yr,and the throw rate is 1.8mm/yr;for wide one (Dali),5mm/yr and 9mm/yr,respectively.It can be estimated from the parameters of fault displacement that recurrence intervals for M6,8 earthquake are 178?29 years.It is consistent with the recurrence intervals (150?50 years) of M 6-7 earthquakes from historic seismic records in this area.It may be useful to immediate-long term earthquake prediction.

The comprehensive characteristics of active faults,physical mechanism of fault basins,pole direction of drainage system and fault plane solution of moderate and small earthquakes indicate that recent tectonic stress fields in the study area trend from NNW to nearly SN.It follows that local tectonic stress fields in the area is related to the tectonic deformation of upper crust,caused by slipping to the south of Sichuan-Yunnan block in which the fault basin in the area has been a pull-apart basin of the surface crust since the Neogene.The boundary faults of the basins tend to be in the form of the shovel and to be down to at a depth of 1-2 km,and moderate/small earthquakes are concentrated at a depth less than 20 km,which suggests a strain release of two sorts at different depths in the slipping process.It is possible that the lower part of the crust is in the process of being deformed to northeast between the large-scele platas.Earthquakes of >M 6 with characteristic of high-angla strik-slip mainly concetate at a depth of 20-25 km which is partly related to NE compressive stress.The intersection of large-scale and local stress fields may be representative of tectonic stress at different depths.Of course,the Hounghuo River fault zone in the presence of shear-tension obviously has an effect on shifting of the stress field direction of this region.

In the coastal area of Southern Fujian,the late Pleistocene sediments have a wide distribution (Fig.1).The late Pleistocene strata are mainly composed of following sediments in ascending order:Dgrey medium-fine sand,2)black mud or peat,and 3)yellow sand and sandy clay.The other possible late Pleistocene deposits,so-called "Old Red Sand",are the semi-cemented,well-sorted,and red quartz silt-fine sand.These deposits are distributed over the bays and gullies of mainland and the islands,and constitute the second terrace,tiebar and other littoral accumulation landforms.In this paper,a number of natural outcrop sections of late Pleistocene strata have been described and drown in Fig.2.Based on the sedimentologic and geomorphologic investigation in the field and the data of ¹⁴C dating (Table 1),analyses of foraminifers and ostracods (Table 2) and pollen analysis (Table 3),the following conclusions can be obtained:1.The grey and yellow sand and sandy clay intercalated with black mud or peat belong to the late Late Pleistocene,i.e.the middle and late pleni-glacial substages of the last Glacial Stage,between about 40,000 and 16,000 years B.P..2.The grey and yellow sand and sandy clay,especially the black mud or peat,of the late Late Pleistocene are mainly the deposits of marine-land transitional facies,in part the littoral,and in part lake and swamp facies.3.On the whole,the climate of the late Late Pleistocene was warm and humid,but sometime cooler and drier.4.The "Old Red Sand" is the littoral sediments which were deposited under the heat and humid climate.It might be deposited during the late stage of Late Pleistocene,but the possibility of forming in the earlier period can not be ruled out.

Since the Late Pleistocene,the movement of the northern segment of the Honghe fault zone has been different from that of the southern one.At the southern segment movement is primarily characteristic of single right-lateral shearing,whereas at the northern segment,of a compositive right-lateral shearing with faulted-depressional extension.With in the compositive zone in question appears an en-echolon fault pattern due to alternate shearing and fault-depression.From the southeast to the northwest,they are: Ding Xiling shearing zone,Dali fault-depression,Xiashankou shearing zone,Eryuan fault-depression,Cibihu Lake shearing zone and Jianchuan fault-depression.Geomorphic feature of shear zone and fault-depression is completely different,the former appearing as a narrow valley and the latter,as a basin.This paper is focused on the determination of displacement rates and recurrence intervals of earthquakes of Dixiling shear zone and Dali fault-depression having remained since the late stages of Late Pleistocene.For Dixiling shearing zone,right-lateral displacement rate is 8mm/yr,and vertical slip rate is 1.8mm/yr,with a ratio of 4:1 and for Dili fault-depression,5mm/yr and 9mm/yr,respectively,with a ratio of nearly 1:2.According to calculations of the parameters of fault displacement,we have found that recurrence intervals for magnitude 6.8 earthquake are 178±29 years.It is consistent with the recurrence interval (150±50 years)of M 6—7 earthquakes from historic seismic records in this area.It may be useful to immediate—long term earthquake prediction.

According to the field investigation along the coastal area of South Fujian and East Guangdong and the ¹⁴C age determinations, a number of stratigraphical profiles are described and ¹⁴C dates of 22 samples published. The subdivision and correlation of the late Quaternary stratigraphy, the Holocene sea level changes and the characteristics of neotectonic movement are preliminarily discussed in this paper.The late Quaternary stratigraphy in this area can be divided into Jiangtian peat and Jingzhou mud belonging to the late Holocene; Zhanglin chenier, Gongqian beachrock and Juewei mud to the Middle Holocene; Xianqian formation of the Early Holocene and Meipu calcareous tufa, Chishan peat, Jiazi buried soil and Houlou formation of the late stage of Late Pleistocene.From the altitudes and C¹⁴ dates of marine beds, beachrock, cheniers as well as sedimentological, geomorphological and biological evidences indicative of the positions of paleosea level, the authors come to the conclusions on the lower stands of sea level in the late stage of late Pleistocene, rising of sea level of the Early-Middle Holocene, and existence of several higher sea levels in the past 6000 years than the present-day's, that were further, proved to be correct. Correlation of altitudes and ages ¹⁴C of samples of this area with representative curves of the Holocene sea level changes, it can be seen that this area can be ascribed to a gentle to moderate uplift one, denying then the idea on the subsiding coast of the South China. Thereby it is also unfavourable to the view on the intense uplift of this area.

Radiocarbon datings indicate that the marine deposits at the depths of 23-40m along coast of Bohai Bay were formed sonn after the slope of the peat development (32000 -22900yr. BP), which can be comparable with the sub-interglacial periods of the last glacial epoch(about 44000-29000yr. B P) and is agreeable with the high sea level period over the whole world in the late stage of the Late Pleistocene (about 35000-23000yr. BP).The lacustrine-swamp peaty deposits or puddly deposits of various thickness have a wide distribution at the depths of 12-16 m beneath the ground surface and 5-6m depth below the Bohai sea floor with 20-30m water depth. In the light of the radiocarbon datings the peaty deposits concerned can be largely placed in Early Holocene (about 10000-8000yr. BP) and named as Lijiabao. Formation, it can be correlated with the Purangdian Formation of Liaonan region. Above the peaty deposits are in succession developed a series of marine sediments. From the radiocarbon datings of shelly bed and oyster-bearing bed in offshore and epicontinental sediments from the underlying peaty deposits and marine sediments, especially from the top of the latter, the marine sediments may be formed in Middle Holocene (about 8000-2500yr. BP) and named as Hou-chengzhuang Formation which can be correlated to the Dagushan Formation of Liaonan region. Most of recent deposits near ground surface are of fluvial facies, and the peaty deposits are also found in the swamp or the ancient river course. From the radiocarbon datings it can be suggested that the marine sediments beyond the Ⅱ chenier ridge along the western coast-of the Bohai Bay and the continental sediments within the Ⅱ chenier ridge both have the age less than 2500yr. belonging to the Late Holocene and correlating to the Zhuanghe Formation of Liaonan region. It is referred to the Qikou Formation.The lithological changes happened in this region and the datings of Holocene deposits indicate that there has been a transgression in Holocene period and sea water arrived at the studied region 7000 years ago. Later on the transgression reached its maximum in the region 6000-5000 years ago when many regions such as Leting, Luannan, Ninghe, Tianjin, Cangzhou, Huanghua and Haixing along the coast of the Bohai Bay are submerged or affected by sea water. About 4000 years ago there was started a regression forming successively the Tongju-Qianmiaozhuang (4700-4000yr. BP), the Zhang-guizhuang -Changzhuang (3800-3000yr. BP), the Baishaling-Nigu-Qikou(2500-1500yr. BP) and the Chengtougu-Dagu chenier ridges (600-500yr. BP).