Soil bentonite wall protects foundation from thrust faulting: analyses and experiment

When seismic thrust faults emerge on the ground surface,they are particularly damaging to buildings,bridges and lifelines that lie on the rupture path.To protect a structure founded on a rigid raft,a thick diaphragm-type soil bentonite wall(SBW) is installed in front of and near the foundation,at sufficient depth to intercept the propagating fault rupture.Extensive numerical analyses,verified against reduced–scale(1 g) split box physical model tests,reveal that such a wall,thanks to its high deformability and low shear resistance,"absorbs" the compressive thrust of the fault and forces the rupture to deviate upwards along its length.As a consequence,the foundation is left essentially intact.The effectiveness of SBW is demonstrated to depend on the exact location of the emerging fault and the magnitude of the fault offset.When the latter is large,the unprotected foundation experiences intolerable rigid-body rotation even if the foundation structural distress is not substantial.     

不同土质条件下断层地表破裂对比研究

本文结合华北地区几个地震统计区的实例,探讨了地震统计区的重要地震活动性参数b值和v4不确定性的主要影响因素及其特征,并研究分析了其不确定性的大小。结果表明,地震活动性参数的不确定性主要影响因素为样本统计时段、样本处理方法、统计下限震级、高震级年平均发生率等。在郯庐地震统计区,b值变化可达0.2以上,v4的变化可达1.4以上,汾渭地震统计区的不确定性也基本相当,河北平原地震统计区因为地震样本相对丰富,不确定性要小许多。     

华北平原强震构造带与潜在震源区划分

在莫尔-库仑理论中引用Drucker-Prager准则,对于基岩断层及其上的覆盖土体建立相应的弹塑性模型,观察在不同力学条件下（张应力、压应力、剪应力）,以及在基岩断层分别为正断或逆断作用下,上覆粉砂质土体和粘土质土体的错动变形。结果表明：在张应力作用下,粘土比砂土更易变形;在压应力作用下,砂土更易变形;而在剪应力作用下,粘土比砂土更易变形,且粘土抗剪强度越大,变形越大。在正断层作用下,在粉砂土与粘性土中所发生的变形并没有大的不同,而在逆断层载荷作用下,粉砂质土体比粘土质土体更容易变形位错。     

Application research of seismic method in assessment of active fault

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Relations between surface deformation,fault geometry,seismicity, and rupture characteristics during the El Asnam (Algeria) earthquake of 10 October 1980

The El Asnam earthquake of October 10, 1980 (M_s=7.3) produced surface faulting on a northeast-trending thrust fault of 30 km length with displacements of up to 6.5 m, though average displacements were about 3 m. In addition, widespread tensional features were formed, some in clear association with folding above the thrust, and others, in an area beyond the exposure of the thrust at the surface, which may be related to buried reverse faults.The observed thrust fault is split into southern, central and northern segments. Local and teleseismic data are examined to show that the main shock nucleated at the southwest end of the fault, and propagated 12 km northeast where a second rupture of approximately equal moment occurred, continuing the faulting a further 12 km northeast along the central segment. Both ruptures nucleated at about 8–10 km depth. Displacements were largest on the central segment, where they were probably enlarged by aftershocks, including one of m_b=6.1 three hours after the main shock. The northern segment was much shorter than the other two, and showed smaller displacement.The junctions between fault segments are marked by distinct geomorphological characteristics and a change in strike of the faulting, as well as a sudden drop in the observed displacement. It appears that the rupture development is influenced by the changes in fault geometry between segments, and that such junctions or barriers have persisted through much of the late Quaternary.     

Microtopographic evolution of mineral surfaces as a tool to identify and date young fault scarps in bedrock

Faulting that results in surface ruptures through bedrock can be particularly difficult to date. For example, stratigraphic control on the age of faulting, based on the age of the bedrock, often leaves unacceptably large uncertainty on the age of the faulting. From a paleoseismological perspective, there is a clear need to determine if a bedrock fault scarp is actually a young feature. For young fault ruptures that create fresh mineral surfaces, analysis of microtopography developed by weathering of the mineral surface may provide a quantifiable method for determining the fault age. The direct quantitative measurement of mineral surface microtopography using Atomic Force Microscopy affords a novel method to study the rupture ages of active faults. The method for using microtopographic evolution of mineral surfaces depends on three conditions. The first condition is that freshly exposed mineral cleavage surfaces, which can be described geometrically as planes, are formed during a rupture event. The formation of these fresh surfaces is analogous to the initiation of a weathering ‘clock’ that defines time t=0. Following cleavage formation dissolution of the planar mineral surface occurs. The rate of dissolution for a mineral species under given climatic conditions, governs the rate of mineral surface alteration. Thus as dissolution proceeds, the roughness of the mineral surface increases. We suggest that the progression of microtopographic roughness over time, which can be estimated by computing quantitative statistics derived from digital mineral surface topography, will systematically vary until a steady state surface topography is reached. The fractal dimension, D_f, is one such measure of surface roughness where, D_f at time t=0 is 2. The dissolution of the mineral surface increases the fractal dimension as the removal of material proceeds. We posit that somewhere between D_f=2 and D_f=3, the microtopography reaches a steady state. Therefore, in the pre-steady state stage of surface roughness, the quantitative measure of roughness of the mineral may serve as a measure of time elapsed since faulting. The period of time this initial stage of surface roughening represents is dependent on the mineral and as a consequence, its dissolution rate, in a specific set of environmental conditions. The time elapsed since fault rupture and grain cleavage can also be estimated from the measurement of the volume of material removed through dissolution. If part of the original cleavage surface remains and can be identified then AFM measurements of the surface microtopography can be used to calculate the dissolved volume per unit area.     

Interaction of a Dynamic Rupture on a Fault Plane with Short Frictionless Fault Branches

Spontaneous bilateral mode II shear ruptures were nucleated on faults in photoelastic Homalite plates loaded in uniaxial compression. Rupture velocities were measured and the interaction between the rupture front and short fault branches was observed using high-speed digital photography. Fault branches were formed by machining slits of varying lengths that intersected the fault plane over a range of angles. These branches were frictionless because they did not close under static loading prior to shear rupture nucleation. Three types of behavior were observed. First, the velocity of both rupture fronts was unaffected when the fault branches were oriented 45° to the main slip surface and the length of the branches were less than or equal to ~0.75 R₀* (where R₀* is the slip-weakening distance in the limit of low rupture speed and an infinitely long slip-pulse). Second, rupture propagation stopped at the branch on the compressive side of the rupture tip but was unaffected by the branch on the tensile side when the branches were ~1.5 R₀* in length and remained oriented 45° to the principle slip surface. Third, branches on the tensile side of the rupture tip nucleated tensile ``wing tip' extensions when the branches were oriented at 70° to the interface. Third, when the branches were oriented at 70° to the interface, branches on the tensile side of the rupture tip nucleated tensile ``wing-crack' extensions. We explain these observations using a model in which the initial uniaxial load produces stress concentrations at the tips of the branches, which perturb the initial stress field on the rupture plane. These stress perturbations affect both the resolved shear stress driving the rupture and the fault-normal stress that controls the fault strength, and together they explain the observed changes in rupture speed.     

23 October 2011 Van, Eastern Anatolia, earthquake (M W 7.1) and seismotectonics of Lake Van area

The 23 October 2011 Van earthquake took place in the NE part of Lake Van area, surprisingly on a fault (the Van fault) that is not present in the current active fault map of Turkey. However, occurrence of such a large magnitude earthquake in the area is not surprising regarding the historical seismicity of the region. The comparison of the damage patterns suggests that the earthquake is much likely a recurrence of the 1715 Van earthquake. The finite fault modelling of the earthquake using teleseismic broadband body waveforms has shown that the earthquake rupture was unilateral toward SW, was mostly reverse faulting, confined to below the depth of 5 km, did not propagate offshore, and was dominated by a failure of a single asperity with a peak slip of about 5.5 m. The total seismic moment calculated for the model is 4.6?×?10¹⁹ Nm (M _W ?≈?7.1). The finite fault model coincides with the field observations indicating blind faulting and the vertical displacements over the free surface estimated from it correlate well with the maximum reported uplift along the coast of Lake Van above the hanging wall. The possible offshore continuations of the Van fault and some other faults lying its south are also discussed by assessing a previous offshore seismic reflection study and the earthquake epicentres and focal mechanisms.     

Coseismic deformation of the 2021 MW7.4 Maduo earthquake from joint inversion of InSAR,GPS, and teleseismic data

The M_W7.4 Maduo earthquake occurred on 22 May 2021 at 02:04 CST with a large-expansion surface rupture. This earthquake was located in the Bayan Har block at the eastern Tibetan Plateau, where eight earthquakes of M_S >7.0 have occurred in the past 25 years. Here, we combined interferometric synthetic aperture radar, GPS, and teleseismic data to study the coseismic slip distribution, fault geometry, and dynamic source rupture process of the Maduo earthquake. We found that the overall coseismic deformation field of the Maduo earthquake is distributed in the NWW-SEE direction along 285°. There was slight bending at the western end and two branches at the eastern end. The maximum slip is located near the eastern bending area on the northern branch of the fault system. The rupture nucleated on the Jiangcuo fault and propagated approximately 160 km along-strike in both the NWW and SEE directions. The characteristic source rupture process of the Maduo earthquake is similar to that of the 2010 M_W6.8 Yushu earthquake, indicating that similar earthquakes with large-expansion surface ruptures and small shallow slip deficits can occur on both the internal fault and boundary fault of the Bayan Har block.     

The erosion rates of cohesive sediments in Venice lagoon,Italy

The stability of cohesive sediments from Venice lagoon has been measured in situ using the benthic flume Sea Carousel. Twenty four stations were occupied during summertime, and a sub-set of 13 stations was re-occupied during the following winter. Erosion thresholds and first-order erosion rates were estimated and showed a distinct difference between inter-tidal and sub-tidal stations. The higher values for inter-tidal stations are the result of exposure that influences consolidation, density, and organic adhesion. The thresholds for each state of sediment motion are well established. However, the rate of erosion once the erosion threshold has been exceeded has been poorly treated. This is because normally a time-series of sediment concentration (C) and bed shear stress (τ₀(t)) is used to define threshold stress or cohesion (τ_crit,z) and erosion rate (E). Whilst solution of the onset of erosion, τ_crit,0, is often reported, the evaluation of the erosion threshold variation through the process of erosion (eroded depth) is usually omitted or not estimated. This usually leads to assumptions on the strength profile of the bed which invariably has no credibility within the topmost mm of the bed where most erosion takes place. It is possible to extract this information from a time-series through the addition of a step in data processing. This paper describes how this is done, and the impact of this on the accuracy of estimates of the excess stress (τ₀(t)–τ_crit,z) on E.     

Tunnel effect of fractal fault and transient S-wave velocity rupture (TSVR) of in-plane shear fault

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Inversion of near-field waveform data for earthquake source rupture process ( II ): Inversion of Chi Chi earthquake source, 20 September, 1999, Taiwan

The new inversion algorithm developed based on the recent progress in the nonlinear programming study by us is used to invert the earthquake source process of Chi Chi earthquake M _w7.6, 20 Semptember, 1999, Taiwan. A curve fault model is constructed in our inversion to make the fault model close to the real rupturing fault to reduce the influence from the discrepancy between the constructed fault model and the real rupturing fault. The results show that (1) the rupture process of the Chi Chi earthquake source lasted about 32 seconds and the main faulting occurred between 6th to 21st second after the start of the ruptures and the high slip area were mainly located at the northern segment of the fault. (2) The slip was dominated by thrust faulting. The average rake angle was 64.5°, which was very consistent with those inverted by USGS, Harvard and CWB (Central Weather Bureau of Taiwan). The amount of the moment inverted in this paper was 7.76×10²⁰ NM, which was a slightly bigger than those inverted by USGS and Harvard. (3) A clear nucleation step existed in the source faulting process and it lasted about 6 seconds. The moment release rate accelerated obviously at the end of the nucleation step. The faulting started from the southern segment and mainly occurred at the northern segment after 10 seconds. At the end of this paper, we analyzed the reliability of the inversion result via comparing with the GPS observations and discussed its scientific signification.     

2014年3月10日加州西北岸M_w6.9级地震震源破裂过程

2014年3月10日13时18分(北京时间)美国加利福尼亚州西北岸发生Mw6.9级地震,震中位于戈尔达板块内部.本文利用国际地震学研究联合会(IRIS)地震数据中心提供的远场体波数据,通过波形反演的方法来研究此次地震的震源破裂过程,并分析未造成重大人员伤亡及诱发海啸的原因,为该地区地球动力学的研究提供依据.选取19个方位角覆盖均匀的远场P波垂向波形记录和13个近场P波初动符号进行约束,基于剪切位错点源模型确定此次地震的震源机制解.结合地质构造背景资料,确定断层破裂面的走向.在考虑海水层多次反射效应的影响下,采用18个远场P波垂向波形数据和21个远场SH波切向波形数据,利用有限断层模型,将断层面剖分为17×9块子断层单元来模拟破裂面上滑动的时空分布,通过波形反演的方法获得此次地震的震源破裂过程.利用海水层地壳模型,剪切位错点源模型的反演结果为:走向323°,倾角86.1°,滑动角-180°,震源深度为10.6km.有限断层模型的反演结果表明,此次地震的破裂过程相对简单,主要滑动量集中于震源上方35km×9km的区域内,破裂时间持续19s左右,平均破裂传播速度约为2.7km·s-1,较大滑动量均沿着走向分布,最大滑动量为249cm.此次地震为发生在戈尔达板块内部的一次Mw6.9级的陡倾角走滑型地震.此次地震为单纯的走滑型地震,断层面接近竖直方向,且发生在洋壳底部,因此破坏力不大,不会对沿岸城市造成重大损失.陡倾角断层在走滑错动的过程中不会使海底地形发生大幅度变化,不会引起大面积水体的突然升降,因此不会诱发大规模海啸.     

Constraints on rupture speed of the 2001 <Emphasis Type="Italic">M</Emphasis><Subscript>S</Subscript> 8.1 West Kunlun Mountain Pass earthquake by co-seismic surface rupture slip displacements based on the slip-weakening mechanism with frictional undershoot involved

With co-seismic surface rupture slip displacements provided by the field observation for the 2001 M_S8.1 West Kunlun Mountain Pass earthquake, this paper estimates the rupture speed on the main faulting segment with a long straight fault trace on the surface based on a simple slip-weakening rupture model, in which the frictional overshoot or undershoot are involved in consideration of energy partition during the earthquake faulting. In contrast to the study of Bouchon and Vallée, in which the rupture propagation along the main fault could exceed the local shear-wave speed, perhaps reach the P-wave speed on a certain section of fault, our results show that, under a slip-weakening assumption combined with a frictional undershoot (partial stress drop model), average rupture speed should be equal to or less than the Rayleigh wave speed with a high seismic radiation efficiency, which is consistent with the result derived by waveform inversion and the result estimated from source stress field. Associated with the surface rupture mechanism, such as partial stress drop (frictional undershoot) associated with the apparent stress, an alternative rupture mechanism based on the slip-weakening model has also been discussed.     

Spatial and temporal rupture process of the January 26, 2001, Gujarat, India, M S=7.8 earthquake

The source parameters, such as moment tensor, focal mechanism, source time function (STF) and temporal-spatial rupture process, were obtained for the January 26, 2001, India, M _S=7.8 earthquake by inverting waveform data of 27 GDSN stations with epicentral distances less than 90°. Firstly, combining the moment tensor inversion, the spatial distribution of intensity, disaster and aftershocks and the orientation of the fault where the earthquake lies, the strike, dip and rake of the seismogenic fault were determined to be 92°, 58° and 62°, respectively. That is, this earthquake was a mainly thrust faulting with the strike of near west-east and the dipping direction to south. The seismic moment released was 3.5×10²⁰ Nm, accordingly, the moment magnitude M _W was calculated to be 7.6. And then, 27 P-STFs, 22 S-STFs and the averaged STFs of them were determined respectively using the technique of spectra division in frequency domain and the synthetic seismogram as Green’s functions. The analysis of the STFs suggested that the earthquake was a continuous event with the duration time of 19 s, starting rapidly and ending slowly. Finally, the temporal-spatial distribution of the slip on the fault plane was imaged from the obtained P-STFs and S-STFs using an time domain inversion technique. The maximum slip amplitude on the fault plane was about 7 m. The maximum stress drop was 30 MPa, and the average one over the whole rupture area was 7 MPa. The rupture area was about 85 km long in the strike direction and about 60 km wide in the down-dip direction, which, equally, was 51 km deep in the depth direction. The rupture propagated 50 km eastwards and 35 km westwards. The main portion of the rupture area, which has the slip amplitude greater than 0.5 m, was of the shape of an ellipse, its major axis oriented in the slip direction of the fault, which indicated that the rupture propagation direction was in accordance with the fault slip direction. This phenomenon is popular for strike-slip faulting, but rather rare for thrust faulting. The eastern portion of the rupture area above the initiation point was larger than the western portion below the initiation point, which was indicative of the asymmetrical rupture. In other words, the rupturing was kind of unilateral from west to east and from down to up. From the snapshots of the slip-rate variation with time and space, the slip rate reached the largest at the 4th second, that was 0.2 m/s, and the rupture in this period occurred only around the initiation point. At the 6th second, the rupture around the initiation point nearly stopped, and started moving outwards. The velocity of the westward rupture was smaller than that of the eastward rupture. Such rupture behavior like a circle mostly stopped near the 15th second. After the 16th second, only some patches of rupture distributed in the outer region. From the snapshots of the slip variation with time and space, the rupture started at the initiation point and propagated outwards. The main rupture on the area with the slip amplitude greater than 5 m extended unilaterally from west to east and from down to up between the 6th and the 10th seconds, and the western segment extended a bit westwards and downwards between the 11th and the 13th seconds. The whole process lasted about 19 s. The rupture velocity over the whole rupture process was estimated to be 3.3 km/s. Foundation item: 973 Project (G1998040705) from Ministry of Science and Technology, P. R. China, and the National Science Foundation of China under grant No.49904004. Contribution No. 02FE2026, Institute of Geophysics, China Seismological Bureau.     

Normal and shear stresses acting on arbitrarily oriented faults, earthquake energy, crustal GPE change, and the coefficient of friction

As usual, earthquake energy is defined as the total energy released from an earthquake, which is partitioned into radiated energy, friction energy, and rupture energy regardless of crustal gravitational potential energy (GPE) change. We analyze the energy and stress parameters in earthquake energy budget. For arbitrarily oriented faults, we deduce the formulas for calculating the normal and shear stresses acting on the fault under principal stresses. We show that shear stress is composed of horizontal and vertical shear stresses. Then, we provide the expressions for computing crustal GPE change and the coefficient of friction. The GPE change should be considered, except strike-slip faulting, when investigating earthquakes. Also, for various faulting types, we show that the ratio of differential stresses is related to the fault orientation and the relative magnitudes of stresses. Finally, “12 May, 2008, Wenchuan, Sichuan, China, M_W 7.9 Earthquake” is cited to analyze and calculate various energy/stress parameters and the coefficient of friction. Our result of GPE change coincides with the post-event field observations.     

Tectonic Features of the M_S8.0 Wenchuan Earthquake and Its Aftershocks

The M8.0 Wenchuan earthquake occurred on the Longmenshan fault zone. Based on field investigation of the surface rupture and focal mechanism study of the aftershocks, we discuss the geological relationship of the main, secondary and triggered ruptures. The main rupture is about 200km long and can be divided into the south part and the north part. The south part consists of two parallel fault zones characterized by reverse faulting, with several parallel secondary ruptures on the hanging wall of the main fault, and the north part is a single main fault zone characterized by lateral strike-slip and reverse faulting. Compared to a 300km long aftershock distribution, the surface rupture only occupies 200km, and the remaining 100km on the northeast of the main rupture was triggered by aftershocks. Study on the ruptures of this earthquake will be useful for studying the earthquake risk evolution on the Longmenshan fault system.     

Distribution of seismic intensities of the November 6, 1988, Lancang-Gengma earthquakes and their surface ruptures in Yunnan Province, China

On November 6, 1988, two earthquakes with magnitude>7 occurred on the Lancang-Gengma fault zone in south-west China. The extensive destruction and loss of lives resulted mainly from widespread collapse of unreinforced masonry and mud brick structures; the maximum preliminary intensity of the Lancang earthquakes was IX on the Chinese scale, which is similar to the Modified Mercall scale, and the highest preliminary intensity of the Gengma earthquake was probably X. The surface manifestation of tectonic activity of the Lancang earthquake was the occurrence of the earthquake-related extensional ground cracks and small fault scarps in the epicentral region. The cracks with small fault scarps occurred mainly in four relatively continuous north-northwest-trending linear zones that ranged from a few hundred meters to 6 km in length. The area within which the cracks and small scarps occurred is 35 km long by 3 km wide. The maximum net throw and the dextral horizontal offset were 1.5m and 1.4m, respectively. Clear evidence of new surface faulting caused by the Gengma earthquake includes a series of relatively continuous north-northwest-trending linear ground crack zones and a 5 km long section of fault scarps. The total length of the surface rupture zones of the Gengma earthquakes is about 24 km, with 3.5m maximum net throw and 3m maximum right-lateral slip. Both earthquakes were associated with surface faulting showing a combination of normal and right lateral motion. The distribution of seismic intensities and surface rupture characteristics of these two earthquakes are discussed in this paper. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 344–353, 1991. The research project was performed out under the direction of Professors. Xingyuan Ma and Yuntai Chen, and the field investigation was performed with help of Kui Jiang and Junchang Zhang of the Seismological Bureau of Yunnan Province. Here the authors express great appreciation.     

IDENTIFICATION OF PALEO-EARTHQUAKES OF LUOYUNSHAN PIEDMONT FAULT BY QUANTITATIVE MORPHOLOGY OF LIMESTONE FAULT SURFACES

The quantitative analysis of morphologic characteristics of bedrock fault surface is a useful approach to study faulting history and identify paleo-earthquake. It is an effective complement to trenching technique, specially to identifying paleo-earthquakes in a bedrock area where the trenching technique cannot be applied. This paper focuses on the Luoyunshan piedmont fault, which is an active normal fault extending along the eastern boundary of the Shanxi Graben, China. There are a lot of fault scarps along the fault zone, which supply plentiful samples to be selected to our research, that is, to study faulting history and identify paleo-earthquakes in bedrock area by the quantitative analysis of morphologic characteristics of fault surfaces. In this paper, we calculate the 2D fractal dimension of two bedrock fault surfaces on the Luoyunshan piedmont fault in the Shanxi Graben, China using the isotropic empirical variance function, which is a popular method in fractal geometry. Results indicate that the fractal dimension varies systematically with height above the base of the fault surface exposures, indicating segmentation of the fault surface morphology. The 2D fractal dimension on a fault surface shows a ‘stair-like’ vertical segmentation, which is consistent with the weathering band and suggests that those fault surfaces are outcropped due to periodic faulting earthquakes. However, compared to the results of gneiss obtained by the former researchers, the characteristic fractal value of limestone shows an opposite evolution trend. 1)The paleo-earthquake study of the bedrock fault surface can be used as a supplementary method to study the activity history of faults in specific geomorphological regions. It can be used to fill the gaps in the exploration of the paleo-earthquake method in the bedrock area, and then broaden the study of active faults in space and scope. The quantitative analysis of bedrock fault surface morphology is an effective method to study faulting history and identify paleo-earthquake. The quantitative feature analysis method of the bedrock fault surface is a cost-effective method for the study of paleo-earthquakes in the bedrock fault surface. The number of weathered bands and band height can be identified by the segment number and segment height of the characteristic fractal dimension, and then the paleoearthquake events and the co-seismic displacement can be determined; 2)The exposure of the fault surface of the Luoyunshan bedrock is affected and controlled by both fault activity and erosion. A strong fault activity(ruptured earthquake)forms a segment of fault surface which is equivalent to the vertical co-seismic displacement of the earthquake. After the segment is cropped out, it suffers from the same effect of weathering and erosion, and thus this segment has approximately the same fractal dimension. Multiple severe fault activities(ruptured earthquake)form multiple fault surface topography. The long-term erosion under weak hydrodynamic conditions at the base of the fault cliff between two adjacent fault activities(intermittent period)will form a gradual slow-connect region where the fractal dimension gradually changes with the height of the fault surface. Based on the segmentation of quantitative morphology of the two fault surfaces on the Luoyunshan piedmont fault, we identified four earthquake events. Two sets of co-seismic displacement of about 3m and 1m on the fault are obtained; 3)The relationship between the fault surface morphology parameters and the time is described as follows:The fractal dimension of the limestone area decreases with the increase of the exposure time, which reflects the gradual smoothing characteristics after exposed. The phenomenon is opposite to the evolution of the geological features of gneiss faults acquired by the predecessors on the Huoshan piedmont fault; 4)Lithology plays an important role in morphology evolution of fault surface and the two opposite evolution trends of the characteristic fractal value on limestone and gneiss show that the weathering mechanism of limestone is different from that of the gneiss.