It is crucial to reveal the surface traces and activity of active faults by obtaining high-precision microtopography and three-dimensional shallow geometry. However, limited by the traditional geological investigation methods in the field and geological condition factors, the measurement method on microtopography and shallow geometry of active fault is badly insufficient. In this study, the TLS and GPR are firstly used comprehensively to delineate the microtopography and shallow geometry of the normal fault scarp on the north margin of Maoyaba Basin in Litang. Firstly, the vertical displacements of two landforms produced by the latest two periods of normal faulting and the two-dimensional GPR profiles are obtained separately. Secondly, the three-dimensional measurement method of active fault based on TLS and GPR is preliminarily established. On this basis, three-dimensional model of fault scarp and three-dimensional images of subsurface geometry are also obtained. These data all reveal a graben structure at normal fault scarps. Thirdly, the fusion and interpretation of three-dimensional data from the surface and subsurface are realized. The study results show:1)the vertical displacements of the T₁ and T₂ terraces by the normal fault movement is 1.4m and 5.7m, the GPR profile shows a typical fault structure and indicates the existence of small graben structure with a maximum width of about 40m in the shallow layer, which further proves that it is a normal fault. 2)the shallow geometry of the normal fault scarp can be more graphically displayed by the three-dimensional radar images, and it also makes the geometry structure of the fault more comprehensive. The precise location and strike of faults F₁ and F₂ on the horizontal surface are also determined in the three-dimensional radar images, which further proves the existence of small graben structure, indicating the extensional deformation characteristics in the subsurface of the fault scarps. Furthermore, the distribution of small graben structure on the surface and subsurface is defined more precisely. 3)the integrated display of microgeomorphology and shallow geometry of normal fault scarp is realized based on the three-dimensional point cloud and GPR data. The fusion of the point cloud and GPR data has obvious advantages, for the spatial structure, morphological and spectral features from the point cloud can improve the recognition and interpretation accuracy of GPR images. The interpreted results of the GPR profiles could minimize the transformation of the surface topography by the external environment at the most extent, restore the original geomorphology, relocate the position and trend of faults on the surface and constrain the width of deformation zones under the surface, the geological structure, and the fault dislocation, etc.
In a word, the TLS and GPR can quickly and efficiently provide the spatial data with multi-level and multi-visual for non-destructive inspection of the microgeomorphology and shallow structure for the active fault in a wide range, and for the detection of active fault in the complex geological environments, and it is helpful to improve the accuracy and understanding of the investigation and research on microtopography and shallow geometry of active faults. What's more, it also offers important data and method for more comprehensive identification and understanding of the distribution, deformation features, the behaviors of active faults and multi-period paleoseismicity. Therefore, to continuously explore and improve this method will significantly enhance and expand the practicability and application prospects of the method in the quantitative and elaborate studies of active faults.

This paper presents a comparison of the calendar range of individual paleoearthquake calculated by conventional calibration,Bayesian analysis of series of peat samples as well as depth-age wiggle matching.The results suggest that: (1)The Bayesian analysis provides an excellent means to enhance chronological resolution when applied to a series of radiocarbon dates from sections with clear stratigraphic relationships.Such application can assess systematic errors when combined with independent chronological information,and determine the optimum chronological information for specific events and contexts.(2)The calendar ranges of series of samples collected from the same peat but different sampling thickness were compared with that of depth-age wiggle matching.The result shows that the chronological resolution by depth-age wiggle matching for the peat sample with thickness less than 2cm could achieve less than 100a.Therefore,the condition to obtain a high resolution calendar age is to have 5～6 samples with 0.5～2cm sampling thickness each and the interval of samples is 0.5～1cm.(3)The calendar range of paleoearthquakes constrained by the Markov chain Monte Carlo(MCMC)Bayesian analysis model,which constructs the order of samples according to their position in the strata with series of radiocarbon dates,was compared with calendar range by the conventional method.The results show that Bayesian analysis could obtain high-precision calendar dates for closely spaced samples.(4)Therefore,the calendar interval of the paleoearthquake event on the middle segment of Huaiyuan Fault was inferred as 1340～1114cal a BP(2σ)by the above systematical comparsion.

According to measuring the natural TT-OSL signals of the fine-grained quartz from both fluvial and lacustrine sediments,the dose recovery experiment and the comparison of the multiple aliquots fine-grained quartz SMAR and Re-OSL dating results,the possibility of Re-OSL dating with fine-grained quartz for water-deposited sediments has been studied.The results show that,the Re-OSL signals accumulated in the fine-grained quartz from fluvial sediments are lack of regularity with the depth,and the Re-OSL signals of the fine-grained quartz can not yield the dose values;While the Re-OSL signals of the lacustrine sediments increase gradually with the depth.The Re-OSL dose measured and laboratory additional dose are consistent within 2%error range,which indicates that the Re-OSL dating with the fine-grained quartz for lacustrine sediments is feasible to some range of time.The Re-OSL dating method has much potential for dating the lacustrine samples more than 100ka years.

Paleoseismic studies conducted along the surface rupture of the Wenchuan earthquake(M_S 8.0)of 12th May 2008 provide important information regarding earthquake reoccurrence intervals and slip rates of the Longmen Shan Fault zone.The Leigu trench was excavated along the middle segment of the surface rupture of the Yingxiu-Beichuan Fault zone.Based on the syntectonic sedimentary structure,two earthquake events,including the Wenchuan event,were identified at this site.This study utilizes Optically Stimulated Luminescence(OSL)dating of samples collected from the Leigu trench section,using SMAR(Sensitivity-corrected Multiple Aliquot Regenerative-dose)protocols.AMS¹⁴C dating was also carried out on charcoal from the same sediments.OSL ages are generally consistent with the calibrated AMS¹⁴C ages(cal a BP)for the same units.The penultimate earthquake event similar to Wenchuan earthquake scale in this region occurred(2.1?0.2)ka to(1.1?0.2)ka.

Equivalent dose(De)preheat plateau test is an often used approach to determine an appropriate preheat temperature in optically stimulated luminescence(OSL)dating. The preheat temperature chosen in OSL dating should be in the plateau region. When the preheat time is fixed as 10s,the De preheat plateau regions are 250～280℃ and 180～260℃ for regeneration dose and test dose respectively for fine-grained quartz in Chinese loess,no matter using single-aliquot regenerative-dose(SAR)protocol or sensitivity change corrected multiple-aliquot regenerative-dose(SMAR)protocol. After reanalyzing the De preheat plateau data derived by SMAR protocol,variation of the ratio of natural OSL intensity to regenerated dose aliquot OSL intensity(N/R)with preheat temperature changes in the similar way with the plot of De as a function of preheat temperature. We suggest that plot of N/R as a function of preheat temperature can be the substitute of De preheat plateau test. This gives us a simple and time-saving approach to determine the preheat temperature in fine-grained quartz OSL dating.

Based on 44 ¹⁴C dates of humic acids and humins under different weather conditions,a statistics analysis was made to estimate their performance in paleosols.The following suggestions are reached:(1)A normal distribution analysis for HA/HM values deduced from 44 ¹⁴C dates results in average value of 0.98 with standard deviation of 0.20.This seems that the humin may be the oldest fraction of soil and its ¹⁴C age can represent the age of the paleosol.(2)The relationship between HA/HM value and the age of paleosol samples shows that the ages of humic acid and humin are indistinguishable for samples deposited in late Quaternary,but are obviously different from paleosol samples in Holocene.Their different behaviors in late Quaternary and Holocene may be related to the pollutant due to Holocene soil exposed to the surface and easily influenced by pollutant.Therefore it is suggested to use the different fractions for Holocene soil to obtain reliable radiocarbon ages for soil samples.(3)Assuming that the modern carbon pollutant entered into soil one-off,the amount of modern carbon into original carbon is estimated to be about 1.49% for late Quaternary soil sample,but this value increases to 21.37% in Holocene soil.Therefore,the amount of pollutant for Holocene soil is over 15 times than that for late Quaternary soil.If such pollutant continues to enter into soil with similar quantity during deposition,the impact percentages are 5.71% and 30.46% for late Quaternary and Holocene soil samples,respectively.The amount of modern carbon by continuously entering into soil is 2.6 times that of the one-off entering into soil for one sample in the same condition.It is further needed to state that which fractions could obtain more reliable ages for soil samples still depends on other factors such as geomorphic location,climatic zone,and soil type.

The reliability of ages from optically stimulated luminescence (OSL) dating of boring core has a stringent dependence on characteristic of samples,and on motheds of boring and sampling. When using a full core collected at boring,the uncertainty of estimation to equivalent dose at OSL dating is affected by some factors,such as mixture occurring in soft soil and sand,contamination due to mud penetrating into sample,the possible influence of heat from pressure and attrition on luminescence signals. In addition,a potential effect on dose rate of samples from boring cores should be emphasized,that is,the effect of change of water content and equilibrium of radioactivity. The basic conditions for sampling,protocols and methods of luminescence dating are important to for sampling correctly in the field. As general requirements for drilling in urban active fault exploration,this paper gives suggestions on sampling from boring core for OSL dating,and factors affecting results of measurement are also discussed.

A Simplified Multiple Aliquot Regenerative-dose (MAR) protocol is introduced in this paper,in which after each natural and regenerative-dose OSL (L_i) measurements,the OSL response (T_i) to the test dose is used to monitor the sensitivity changes for multiple aliquots as Single-Aliquot Regenerative-dose (SAR) protocol does on single-aliquot. From the methodological aspects,Simplified MAR protocol can correct for the sensitivity changes,overcome the scattering of the experimental data in MAR measurement procedures and possibly avoid the buildup of OSL signals that happens in the SAR protocol; these lead to recover De values with high accuracy and precision. When comparing the OSL ages obtained in this way with the reference age of the M IS5/4 transition from the SPECMAP record,no apparent age underestimation occurred. On the basis of the methodology and validated by dating reference age samples,Simplified MAR protocol is a reliable and timesaving way for luminescence dating of fine-grained quartz in Chinese loess.

Previous results about the magnitude and rate of strike-slip movement along the eastern segment of the Altun Fault are quite inconsistent with each other. This is mostly because that the Quaternary strike-slip rate was inferred mainly from the offset of drainage system or from interglacial sediments,while these data focused mainly on late Quaternary. Tracing the early Pleistocene alluvial gravel bed outcropped along the easternmost segment of the Altun Fault,we discovered that the western boundary of the ancient alluvial fan deposits of the Shulehe River is now about 10km away from the outlet of the river. We believe that this is an important evidence indicating that the Quaternary left-lateral strike-slip displacement along the easternmost segment of the Altun Fault is about 10km. Basing on the analysis of terraces at the outlet of the Shulehe River,we conclude that the 2.8km elbow-like winding of the Shulehe River channel along the Altun Fault indicates not only the left-lateral strike-slip of the Altun Fault,but also the effect of lateral erosion at the meander reach of the river. The magnitude of the Quaternary dislocation and slip rate along the easternmost segment of the Altun Fault are discussed in this paper as well.

The ages of terrace deposits along the Shulehe River system are determined by the use of Optical Stimulated Luminescence (OSL) dating technique. The possible tectonic implications of the obtained age data are discussed as follows: (1) The Duanjiagou,Shulehe,and Tashihe Rivers are three rivers of different characters from the Shulehe River system. Several levels of terraces of different altitudes and corrosion rates were developed in the intermont basin and mountain front on the eastern segment of the Altyn Tagh fault. These terraces are the result of differential uplift of the fault blocks. (2) On the southern margin of the Changma basin,7 levels of terraces were developed along the Shulehe River. OSL dating results show that those over 100m high terraces were formed mainly about 40000 years ago,and this may indicate the intensive uplift of the Daxueshan-Xiangmaoshan Mountains and the new activity of the Changma seismic belt. The rate of tilted uplift of the southern part of the Changma basin is inferred to be 2.5mm/a. (3) At Zhaobishan gorge,five levels of terraces of the Shulehe River are still well preserved. Among them,the T₃ terrace of 40～60m elevation above the stream level might be related to the new tectonic activity of the region. The T₅ terrace of over 150m elevation above the stream level observed at the boca has an ESR age of approximately 200ka and an uplift rate of 0.7mm/a. (4) On the Hongliuxia fault block uplift,4 levels of terraces were developed along the Duanjiasha River. Dating results of the T₁,T₂ and T₃ terraces show that a linear relation exists between the heights and the ages of the terraces,from which an uplift rate of 0.6mm/a can be deduced. The Hongliuxia and the Zhaobishan fault block uplifts are the fault blocks controlled by the strike-slip movement of the Altyn Tagh Fault. They have approximately the same rate of uplift that is quite different from that of the range-front uplift of the Daxueshan-Xiangmaoshan Mountains,indicating that the uplift deformation of the Tibetan Plateau in the late stage of late Pleistocene occurred mainly along the Changma active fault zone. (5) Four levels of terraces were developed at the fan apex of the Tashihe River,and the age of the T₃ terrace is dated to be 78.8±5.5ka. It is postulated,therefore,that the terraces at the apex of the Tashihe River alluvial fan were formed in the middle to late stages of late Pleistocene. On the basis of OSL dating results of terrace deposits and the investigation of tectonic landforms,it is concluded that periodic uplift has occurred in the Nanjieshan fault block at 300 ka BP or during the middle to late stage of late Pleistocene.

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.

Along the Dashuichang gouge profile of the Yishu fault zone, there are ten divided gouge stripes based on colors and textures of the gouge Thirteen samples for ESR dating have been collected from the various gouge stripes ESR dates of these samples range from 240ka to 530ka B P, and concentrated on two time intervals of 240～310ka and 410～530ka, respectively It means that there might be two major active episodes on the fault during the Quaternary period. The ESR dates of gouge quartz samples are consistent with geological evidence and intersection relationship on outcrop section.

Seven samples of wind blow,glaciofluvial and fluvial sediments are collected from northern Tianshan Mountain Each sample is dated for fine grain using the the luminescence techinque to get three paleodose of TL,GLSL and IRSL Comparison of the paleodoses shows that they are in agreement for win blow samples,but different for the the samples that were not totally bleached before sedimented The paleodose of TL is larger than those of GLSl,IRSL

Two peat samples collected from Dawangzhuang section,Yanqing basin were treated with NaClO,NaOH solution,Na₄P₂O₇-NaOH soultion and organic soultion,respectively and then ten different organic fractions were obtained from each peat sample. The radiocarbon age of each fraction was obtained and compared to evaluate the accuracy and reliability of the radiocarbon dating age of each fraction.

The Yanqing faulted basin has been developed since the late Cenozoic.It is confirmed that there are lake Quaternary sediments in the basin.ESR technique was used to date samples of the caliche in lake deposit exposed on the surface from the Yanqing basin, Beijing.The results indicate that it is possible to date caliche by using ESR technique,and the estimate of age for the lake deposit in question has been conducted.

In this paper we describe our efforts to determine relative motion of different blocks duringthe Quaternary period by using paleomagnetic method. The Ordos and Longxi blocks,on whichLuochuan and Jiuzhoutai loess profiles lie respectively,are selected for the study.Luochuan andJiuzhoutai loess profiles are complete and comparable in age of loess-paleosol sequences;Samplesfor paleomagnetic measurement were collected from 4 loess layers of these two profiles:upperpart of L₁,bottom of L₁, bottom of L₅ and bottom of L₁₅.The age of these layers is 15 ka B.P.,85 ka B.P.,and 1.1Ma B.P.respectively.The Ordos block is considered to be motionless;The virtual geomagnetic pole(VGP)posi-tion of different periods was obtained from paleomagnetic measurements of each layer on Lu-ochuan profile and its location. Paleomagnetic declinations expected(D_ex)of Lanzhou were calcu-lated from VGP position and the location on Jiuzhoutai profile.There are differences between de-clination expected(D_ex)and declination observed(D_ob )in different periods. The differences are-0.7±5.2°,-1.8±2.4°,-4.1±3.8°and-9. 0±4.7°。It indicates that Longxi Block hasundergone clockwise rotation relative to the Ordos Block since 1.1 Ma B. P. The mean rotationrate is about 0.5′/ka.

Activity and neotectonics of the Shenzhen fault zone in the Shenzhen Special Economic Zone,Guangdong Province,has been discussed on the basis of geomorphic features and Quaternary sediments,as follows:1. There is a series of the smaller intermontane basins and valleys,with axis orientation of NE-SW or ENE-WSW same as trending of the major faults within the fault zone. Most of these basins and valleys,in which the colluvium,alluvium and swamp deposits,with a total thickness of less than 10-15m,were accumulated during the period from the middle of the Late Pleistocene to the middle of the Holocene,are located in the older fracture and or the limistone strata undergoing karstification strongly. Their distribution,hence,might be related to the faulting processes before the Late Pleistocene. However,any fault and marked deformation in the sediments of the Late Pleistocene and Holocene has not been observed. It may be suggested that no remarkably faulting has occurred in the fault zone at least since the middle of the Late Pleistocene.2. Four paleo-denudation surfaces and three alluvium tarraces have been developed in the fault zone since about 1.8 Ma. The vertical deformation rates of crust uplift relative to the regional erosion basis could be estimated as 0.04-0.2mm/a for different ages,based upon the elevations and duration estimates of the geomorphic surfaces formed in different stage. The Quaternary tectonic movement would be characcterized by pulse uplift and depression of the crust for the Shenzhen fault zone.