Examining the spatial and temporal distribution of seismic activity holds significant importance for seismic risk assessment, particularly in regions prone to frequent and intense earthquakes such as the Sichuan-Yunnan region in China. It is widely recognized that earthquakes exhibit non-random patterns in both spatial and temporal dimensions.

Early scientists endeavored to predict earthquakes using statistical principles, leading to the development of various forecasting methods. Among these, the Relative Intensity(RI)and Pattern Informatics(PI)methods emerged as statistical approaches to earthquake prediction modeling. Essentially, both methods fall under the category of smoothing seismic activity models. They employ techniques to quantify temporal changes in seismic activity graphs, generating maps that highlight areas(hot spots)where earthquakes may occur during specific future periods. While the RI algorithm’s theory is straightforward, its forecasting efficacy is robust, particularly notable in predicting major earthquakes, demonstrating similar advantages to the PI algorithm. Widely adopted globally for proactive predictions across diverse tectonic systems, it has shown commendable results in seismic forecasting practices both domestically and internationally. Over years of development, its predictive performance has gained prominence. However, further research is needed to assess its suitability for predicting minor seismic events in low-seismicity zones. Additionally, its successful application hinges on background seismic activity and the selection of target magnitudes.

To aid seismic activity prediction in the Sichuan-Yunnan region and identify potential future seismic source areas, a comprehensive parameter analysis was conducted using the Relative Intensity(RI)algorithm with the parameter traversal test(PTT). The RI algorithm operates on the premise that the predicted intensity of future earthquakes in a given region closely mirrors the intensity of past earthquakes. While it may not explicitly consider the “active” and “quiet” characteristics of seismic activity, as a fundamental prediction algorithm, it often yields improved prediction outcomes when applied to assess seismic probability in regions with high seismic activity, such as the Sichuan-Yunnan region.

In this study, the statistical-based Relative Intensity(RI)algorithm is employed to calculate the relative intensity of earthquakes based on quantitative earthquake characteristics. The study involves gridding the investigated area and statistically analyzing historical earthquake occurrences within each grid unit under specific magnitude conditions to inform predictions of future earthquake frequencies. The research focuses on evaluating the influence of four key model parameters: grid size, length of the anomalous learning window, starting point of the prediction window, and length of the prediction window, on the algorithm’s prediction efficiency. Furthermore, the study investigates the applicability of the RI algorithm to the Sichuan-Yunnan regions in China. The results yield two significant findings:

(1)The integration of the Relative Intensity(RI)algorithm with the Parameter Traversal Test(PTT)yielded significantly improved results compared to random guessing, primarily due to its optimized parameter selections. These parameters include the grid size, length of the anomalous learning time window, starting time of the prediction time window, and length of the prediction time window.

(2)The parameters of the prediction model exhibit a degree of stability and demonstrate predictive capability for seismic activity in the Sichuan-Yunnan region over the next 1-5 years. The study revealed specific rules and effective parameter intervals applicable to earthquake-prone areas in Sichuan-Yunnan.

The findings suggest that the integration of the Relative Intensity(RI)algorithm with the Parameter Traversal Test(PTT)holds promise for predicting seismic activities in the Sichuan-Yunnan region. This approach enhances the pool of references available for predicting earthquake trends in regions prone to frequent and intense earthquakes. Further research on the RI algorithm is anticipated to yield a more refined numerical model for earthquake trend prediction, contributing to enhanced forecasting accuracy and preparedness in earthquake-prone areas.

The Longmenshan fault zone is located in the northeastern margin of the Qinghai-Tibet plateau, with an overall direction of NNE and a total length of about 500km. As we have known, the Longmenshan fault zone is the boundary fault between the Bayanqala block and Sichuan basin. Since the Cenozoic, the Longmenshan fault zone has experienced intense tectonic activity and multi-stage magmatic activity, forming a series of active faults with different scales and properties.

And Lushan M_S7.0 earthquake in 2013 and Lushan M_S6.1 earthquake in 2022 occurred in the southern section of Longmenshan fault zone, and the two earthquakes were only 10km far away apart. The generation of the two strong earthquakes is closely related to the seismic tectonic environment and crustal physical structure parameters. So to study the characteristics of shallow crustal physical structure and its relationship with deep dynamic processes, is good for us to understand the seismogenic environment of this area. The wide angle inverse/refraction detection method is an effective means to obtain the physical property parameters of the crust. In this paper we extracted the first arrival travel time data of P-wave and S-wave from Jinchuan-Lushan-Leshan deep seismic sounding(DSS)profile data. The 2D ray-tracing travel-time imaging method proposed by Zelt et al.(1998)was used to obtain the 2D P-wave, S-wave and Poisson’s ratio structure of the upper crust in the source area of the Lushan strong earthquake and its adjacent area. Then based on the results of deep crust exploration, seismic distribution characteristics and other geophysical and geological studies in this area, we focus on the response of shallow tectonic environment and deep dynamic processes in the upper crust, and analyze the seismogenic environment and seismogenic mechanism of M6-7 strong earthquakes in this area. The results show that: 1)The crustal velocity and Poisson’s ratio are significantly different at different positions of the profile. In the Songpan-Ganzi block, the velocities of P- and S-waves in the upper crust are relatively high and the Poisson’s ratio is relatively low. While in the Sichuan basin, the velocities of P- and S-waves in the upper crust are relatively low and the Poisson’s ratio is relatively high. In Longmenshan tectonic belt which between the Songpan-Garze block and the Sichuan basin, the velocities of P- and S-waves and Poisson’s ratio isolines of the upper crust are controlled by regional tectonic activities, which are basically consistent with the occurrence of the strata and show a near-vertical trend. The sedimentary basement below the tectonic transition zone shows obvious structural differences, and the velocity and Poisson’s ratio contour lines form “V” shape characteristics. 2)The characteristics of high crust velocity and low Poisson ratio(<0.26) in the Songpan-Ganzi block may be the direct reflection of the strong deformation of Sinian-Paleozoic strata caused by the orogenic activities in the northeastern margin of the Qinghai-Tibet plateau in the Indosinian period, and the bi-direction contraction of the strata in the Triassic Xikang Group, the obvious thickening of the crust, and the multi-stage magmatic activities. 3)The large lateral variation gradient of velocity and Poisson’s ratio in Longmenshan tectonic belt between Songpan-Ganzi block and Sichuan basin is the direct evidence of vertical crustal deformation caused by the compression of low Poisson’s ratio crust from the eastern margin of Qinghai-Tibet plateau to the hard Yangzi platform(high Poisson’s ratio)by the remote effect of the collision between the Indian plate and the Asian plate since late Quaternary. 4)The aftershocks of the M_S7.0 earthquake mainly occurred on the high-velocity and Low-Poisson’s ratio side of the velocity and Poisson’s ratio gradient belts in the crust. The seismicity in this area is not only controlled by the regional fault structure, but also closely related to the physical structure characteristics of the upper crust.

The Yangtze fault zone is a typical tectonic regime transition zone of the eastern China. Tectonically, it is characterized by alternated rifts and uplifts and “several crystalline basements with one sediment cover”. Abundant metal metallogenic deposits are developed. Improvement of the velocity model and basement structure will benefit our understanding and knowledge about the regional tectonics. Large volume airgun sources have been broadly applied to seismic surveys due to significant advantages. For instance, they are environmentally friendly, use lower frequencies, and are repeatable. Several seismic and geological research institutions, such as China Earthquake Administration, carried out a three-dimensional comprehensive sounding using the large volume airgun as the seismic source which was fired at the channel of the Yangtze River in 2015. The source-receiver geometry of this seismic experiment covered the whole Anhui Province which locates at the Middle-Lower Yangtze River. The densest observational area is in the Middle-Lower Yangtze River Metallogenic Belt which is a narrow area along the Yangtze River and consists of the Luzong, Tongling, Ningwu, and Anqing-Guichi ore deposits. The Tanlu fault zone, a giant strike-slip fault of more than 2 000km long, passes through the northwestern margin of this area. Geophysical studies have demonstrated copious geological evidences for the Yangtze fault zone, which is approximately 450km long and crosses central China, extending to the eastern coastal area. The present fault and fold systems are the consequences of the repeated tectonic events since the Mesozoic. We collected and analyzed the seismic data of 20 fixed airgun shot points, then utilized tomography, time term method and head wave traveltime inversion based on ray tracing techniques to model the upper crustal velocity and crystalline basement structure of the Anqing-Maanshan segment beneath the Yangtze fault zone. The profile along the Yangtze River consists of 100 PDS-2 seismometers with a spacing of 2km. We applied the linear and phase weighted stack methods to improve the signal-to-noise ratio of the weak seismic phases from the airgun source. According to the comparison between the linear and phase weighted stack results, the phase weighted stack method significantly improves the quality of the stacked data. We applied the band-pass filter to the stacked data to improve the onset of the first arrival, then picked up the seismic phases and assessed the errors of the picked traveltime. The comprehensive results reveal that the upper crust velocity structure and crystalline basement images show a tectonic feature of alternating rifts and uplifts. The upper crust of the Huaining Basin is the thickest area along the Yangtze River. The basement of the Huaining Basin is around 4.5km and there are Mesozoic lacustrine sedimentary layers whose thickness is about 2km. The crystalline basement depth of the Luzong Basin is 4.1km and the consolidated basin shows clear depression basin shape. This feature of the Luzong Basin reveals that it experienced extensional depression. There is a high-velocity zone beneath the crystalline basement of the Luzong Basin, and the velocity is higher than other areas along the Yangtze River. This high velocity zone shows an arc shape, which agrees with the Paleozoic reflection images by the seismic reflection survey. The profile crosses the Yangtze River in Tongling area and there are obvious velocity differences between the two sides of the Yangtze River. The velocity differences show that the Yangtze faults cut the crystalline basement in Tongling. The upper crust velocity structure of the Tongling area shows clear uplift features and its crystalline basement depth is about 2.2km, which agrees with the arc-reflection structures of the upper crust from the seismic reflection data. This uplift image reveals that the upper crust of the Tongling area has experienced extrusion deformations. The consistency of the seismic reflection imaging results with the near surface geology demonstrates that the large volume air-gun source is applicable to land-based seismic survey.

The urban active fault survey is of great significance to improve the development and utilization of urban underground space, the urban resilience, the regional seismic reference modeling, and the natural hazard prevention. The Beijing-Tianjin metropolitan region with the densest population is one of the most developed and most important urban groups, located at the northeastern North China plain. There are several fault systems crossing and converging in this region, and most of the faults are buried. The tectonic setting of the faults is complex from shallow to deep. There are frequent historical earthquakes in this area, which results in higher earthquake risk and geological hazards. There are two seismicity active belts in this area. One is the NE directed earthquake belt located at the east part of the profile in northern Ninghai near the Tangshan earthquake region. The other is located in the Beijing plain in the northwest of the profile and near the southern end of Yanshan fold belt, where the 1679 M8.0 Sanhe-Pinggu earthquake occurred, the largest historical earthquake of this area. Besides, there are some small earthquake activities related to the Xiadian Fault and the Cangdong Fault at the central part of the profile.
    The seismic refraction experiment is an efficient approach for urban active fault survey, especially in large- and medium-size cities. This method was widely applied to the urban hazard assessment of Los Angeles. We applied a regularized tomography method to modeling the upper crustal velocity structure from the high-resolution seismic refraction profile data which is across the Beijing-Tianjin metropolitan region. This seismic refraction profile, with 185km in length, 18 chemical explosive shots and 500m observation space, is the profile with densest seismic acquisition in the Beijing-Tianjin metropolitan region up to now. We used the trial-error method to optimize the starting velocity model for the first-arrival traveltime inversion. The multiple scale checker board tests were applied to the tomographic result assessment, which is a non-linear method to quantitatively estimate the inversion results. The resolution of the tomographic model is 2km to 4km through the ray-path coverage when the threshold value is 0.5 and is 4km to 7km through the ray-path coverage when the threshold value is 0.7. The tomographic model reveals a very thick sediment cover on the crystalline basement beneath the Beijing-Tianjin metropolitan region. The P wave velocity of near surface is 1.6km/s. The thickest sediment cover area locates in the Huanghua sag and the Wuqing sag with a thickness of 8km, and the thinnest area is located at the Beijing sag with a thickness of 2km. The thickness of the sediment cover is 4km and 5km in the Cangxian uplift and the Dacang sag, respectively. The depth of crystalline basement and the tectonic features of the geological subunits are related to the extension and rift movement since the Cenozoic, which is the dynamics of formation of the giant basins.
    It is difficult to identify a buried fault system, for a tomographic regularization process includes velocity smoothing, and limited by the seismic reflection imaging method, it is more difficult to image the steep fault. Velocity and seismic phase variations usually provide important references that describe the geometry of the faults where there are velocity differences between the two sides of fault. In this paper, we analyzed the structural features of the faults with big velocity difference between the two sides of the fault system using the velocity difference revealed by tomography and the lateral seismic variations in seismograms, and constrained the geometry of the major faults in the study region from near surface to upper crust. Both the Baodi Fault and the Xiadian Fault are very steep with clear velocity difference between their two sides. The seismic refraction phases and the tomographic model indicate that they both cut the crystalline basement and extend to 12km deep. The Baodi Fault is the boundary between the Dachang sag and the Wuqing sag. The Xiadian Fault is a listric fault and a boundary between the Tongxian uplift and the Dachang sag. The tomographic model and the earthquake locations show that the near-vertical Shunyi-Liangxiang Fault, with a certain amount of velocity difference between its two sides, cuts the crystalline basement, and the seismicity on the fault is frequent since Cenozoic. The Shunyi-Liangxiang Fault can be identified deep to 20km according to the seismicity hypocenters.
    The dense acquisition seismic refraction is a good approach to construct velocity model of the upper crust and helpful to identify the buried faults where there are velocity differences between their two sides. Our results show that the seismic refraction survey is a useful implement which provides comprehensive references for imaging the fault geometry in urban active fault survey.

In recent years, strong earthquakes of M_S8.0 Wenchuan and M_S7.0 Lushan occurred in the central-southern part of Longmenshan fault zone. The distance between the two earthquakes is less than 80 kilometers. So if we can obtain the inner structure of the crust and upper mantle, it will benefit us to understand the mechanism of the two earthquakes. Based on the high resolution dataset of Bouguer gravity anomaly data and the initial model constrained by three-dimensional tomography results of P-wave velocity in Sichuan-Yunnan region, with the help of the preconditioned conjugate gradient(PCG)inversion method, we established the three dimensional density structure model of the crust and upper mantle of the central-southern segment of Longmenshan, the spatial interval of which is 10 kilometers along the horizontal direction and 5 kilometers along the depth which is limited to 0~65km, respectively. This model also provides a new geophysical model for studying the crustal structure of western Sichuan plateau and Sichuan Basin. The results show obvious differences in the crustal density structure on both sides(Songpan-Ganzê block and Sichuan Basin)of Longmenshan fault zone which is a boundary fault and controls the inner crustal structure. In Sichuan Basin, the sedimentary layer is represented as low density structure which is about 10km thick. In contrast, the upper crust of Songpan-Ganzê block shows a thinner sedimentary layer and higher density structure where bedrock is exposed. Furthermore, there is a wide scale low density layer in the middle crust of the Songpan-Ganzê block. Based on this, we inferred that the medium intensity of the Songpan-Ganzê block is significantly lower than that of Sichuan Basin. As a result, the eastward movement of material of the Qinghai-Tibet plateau, blocked by the Sichuan Basin, is inevitably impacted, resulting in compressional deformation and uplift, forming the Longmenshan thrust-nappe tectonic belt at the same time. The result also presents that the crustal structure has a distinct segmental feature along the Longmenshan fault zone, which is characterized by obviously discontinuous changes in crustal density. Moreover, a lot of high- and low-density structures appear around the epicenters of Wenchuan and Lushan earthquakes. Combining with the projection of the precise locating earthquake results, it is found that Longmenshan fault zone in the upper crust shows obvious segmentation, both Wenchuan and Lushan earthquake occurred in the high density side of the density gradient zone. Wenchuan earthquake and its aftershocks are mainly distributed in the west of central Longmenshan fault zone. In the south of Maoxian-Beichuan, its aftershocks occurred in high density area and the majority of them are thrust earthquake. In the north of Maoxian-Beichuan, its aftershocks occurred in the low density area and the majority of them are strike-slip earthquake. The Lushan earthquake and its aftershocks are concentrated near the gradient zone of crustal density and tend to the side of the high density zone. The aftershocks of Lushan earthquake ended at the edge of low-density zone which is in EW direction in the north Baoxing. The leading edge of Sichuan Basin, which has high density in the lower crust, expands toward the Qinghai-Tibet Plateau with the increase of depth, and is close to the west of the Longmenshan fault zone at the top of upper mantle. Our results show that there are a lot of low density bodies in the middle and lower crust of Songpan-Ganzê Block. With the increase of the depth, the low density bodies are moving to the south and its direction changed. This phenomenon shows that the depth and surface structure of Songpan-Ganzê Block are not consistent, suggesting that the crust and upper mantle are decoupled. Although a certain scale of low-density bodies are distributed in the middle and lower crust of Songpan-Ganzê, their connectivity is poor. There are some low-density anomalies in the floor plan. It is hard to give clear evidence to prove whether the lower crust flow exists.

By using moving average method to separate Bouguer gravity anomaly field in Sichuan-Yunnan region, we got the low-frequency Bouguer gravity anomaly field which reflects the undulating of Moho interface. The initial model is obtained after seismic model transformation and elevation correction. Then, we used Parker method to invert the low-frequency Bouguer gravity anomaly field to obtain the depth of Moho interface and crustal thickness in the area. The results show that the Qinghai-Tibet block in the northwest of the study area deepens and thickens from the edge to the interior, with the depth of Moho interface and the crust thickness of about 52~62km and 54~66km, respectively. The depth of Moho interface in Sichuan Basin is about 38~42km. In Sichuan-Yunnan block, the depth of Moho interface is about 42~62km from southeast to northwest. Beneath the West Yunnan block, west of the Red River fault zone, the Moho depth is about 34~52km from south to north. The Longmen Mountains and Red River fault zone are the gradient zone of the Moho depth change. Along the Red River fault zone, the depth difference of Moho interface is increasing gradually from north to south. No obvious uplift is found on the Moho interface of Panzhihua rift valley. The depth of Moho interface distribution in Sichuan and Yunnan is obviously restricted by the collision between the Indian plate and the Eurasian plate and the lateral subduction of the Indo-China peninsula. The mean square error of the depth of Moho interface is less than 1.7km between the result of divisional density interface inversion and artificial seismic exploration. At the same time, we compared the integral with divisional inversion result. It shows that:in areas where there is obvious difference between the crust velocity and density structure in different tectonic blocks, the use of high resolution seismic exploration data as the constraints to the divisional density interface inversion can effectively improve the reliability of inversion results.

The Red River Fault in western Yunnan is one of the longest strike-slip faults in China and has a high seismic potential. To investigate its complicated structure, a near-NS directed 300km long wide-angle reflection/refraction seismic profile was laid out from Yunxian to Ninglang, across the Red River Fault. The 2-D velocity structure model along the profile was obtained through 1-D and 2-D analysis and fitting the observed data with combination of first-arrival traveltime tomography and forward modeling. The results indicate:In the crust, the average P-wave velocity is 6.2~6.3km/s and basically shows a positive gradient structure, but there are some low velocity anomalies at different area in upper and lower crust. Regarding the crust boundary, a relative large lateral variation exists in the depth of Moho, which goes deeper from south to north, ranging from 45km to as deep as 54km; compared to other typical continental crust, the study area demonstrates a striking thickening. It should be mentioned that the crustal thickening is mainly observed in the lower crust, while the upper and middle crust possess nearly constant thickness. We observed strong seismic velocity contrast across the Red River Fault, which emphasizes the role of the fault as an important tectonic boundary between Yangtze paraplatform and Sanjiang geosynclinal system. Along the profile, the Moho depth has no remarkable variation when crossing the Red River Fault. Combining with other study results on nearby area, it proves that there is notable heterogeneity between different parts of the Red River Fault.

In this paper the crustal velocity structure is obtained along Yushu earthquake zone, using wide angle reflection and refraction data. The results reveal strong vertical and lateral heterogeneities in the crust, as well as the basic characteristics of the crustal velocity structure and the tectonics along the seismic sounding profile. Results show that crustal velocity structure is featured with significant regional heterogeneity both in the longitudinal and lateral directions. The crust is of layered structure, and the crystalline basement interface undulates greatly beneath the study area, which is about 8 km in thickness beneath Yushu and gradually thins northwards to 2.5 km beneath the Stake 400.0 km at Wenquan. There are good correlations of the depressions and uplifts on basement interface with different tectonic units. The crust gradually thins towards both south and north direction to a thickness of 62 km from 72 km beneath Nangqian and Yushu. There exist big undulations in 2D velocity contours and the interfaces in the crust between Stakes 200.0～400.0km, and there is presence of an arc-shaped depression in the Moho beneath the Yushu area.

DSS data of Bohai Bay profile was processed in August 2011 and the result obtained in this paper and the results of other profiles,which cross this profile,were interpreted comprehensively in this paper. The DSS data were calculated and interpreted synthetically using 1-D and 2-D processing techniques in order to find out the basic features of 2-D velocity structures,spatial distribution of faults,geological structure of shallow and deep crust in the southwest margin of Bohai Bay and adjacent areas. The result shows that obvious layered structure appears along the profile,and the crustal velocity structures in different regions have obvious heterogeneity in the lateral and vertical directions. The crystalline basement near the Bohai Bay is gradually thinning southwestwards,and beneath the 220km Stake,the depth of G interface is 7.4km. The thickness of the middle layer varies greatly,with the change range up to 4.0km. The crustal depth varies relatively moderately,with a change range of about 2.0km. The Moho deepens gradually from coastal area to the inland along the southwest direction.

The Weihe Fault is an important blind fault in Weihe Basin and controls the formation,evolution and seismicity of Weihe Basin. The deep seismic reflection survey results show that the fault is not a deep crustal fault; it is located right below the C layer at about 15km depth and cuts through the crystalline basement and the C layer,causing a throw of about 4km between the two sides of crystalline basement. The dip angle at the shallow part of the fault(depth<5km)is big and flattens with depth,and the fault turns to be a listric fault.Shallow seismic survey results show that the dip angle of the Weihe Fault in the middle and deep parts is about 85°; the attitude is different on the two walls of the fault,the footwall is horizontal and the hanging wall is tilting to the south direction; and its dip angle increases quickly.Drilling survey results show that the fault at the shallow part is obviously manifested. The lithology,thickness and attitudes of strata are quite different between the two sides of fault. The attitude on the footwall is horizontal and that on the hanging wall tilts a bit to the fault side. The late Pleistocene displacement is about 4～6m.Trenching results show that the Weihe Fault near ground is still active. Since Holocene epoch it has undergone 3 paleoearthquakes and 1 history earthquake,so it is a Holocene active fault.

Obvious differences of crustal structures exist in different tectonic blocks of China's continent. These differences can be found mainly in crustal stratification, structural features of the upper and lower crust, degree of crustal heterogeneity, properties of crust-mantle boundaries, distributions of crustal low-velocity layers and the interfaces within the crust, especially the tectonic forms of the Moho. These differences of crustal structures reflect the differences of deformation features and geodynamic processes within the crust of these regions, and may provide some constraints for delineating active tectonic blocks. The descriptions of the degrees of heterogeneities of the active tectonic blocks will help to understand the probabilities of decoupling of these tectonic blocks at different depth levels. The mode of motion of these active blocks is controlled by the behavior of their boundaries and the contacting styles of the blocks. Most of the strong earthquakes in China occur near the boundary belts of these active tectonic blocks. A wide-angle reflection and refraction profile about 1 000km long was deployed in 1999, which crosses through Bayan Har fold belt, Qinling-Qilianshan fold belt, Haiyuan strong earthquake region and Ordos block from southwest to northeast. From the analysis of these data, fine structural models of the crust for the eastern edge of Tibet plateau and Ordos block were established, and the results were compared with those of North China. The differences of crustal structures in Bayan Har block of eastern Kunlun at the northeastern edge of Tibet Plateau, Ordos block and Tangshan earthquake region in North China, as well as their relationships to strong earthquakes are discussed in this paper.

Research on a large number of seismic events at home and abroad has indicated that tremendous earthquake hazards in urban areas are mostly attributed to earthquakes caused by active faults buried beneath the cities. The identification of urban buried active faults, therefore, is an important and urgent task. High-resolution seismic exploration is an effective geophysical technique that can be used to identify urban buried active fault at present. High-resolution seismic exploration for urban buried active faults is a sophisticated and systematic project, which involves excitation and receiving techniques, observational system, as well as seismic data processing and interpretation. The seismic source is of the first importance among the other problems that should be solved during the exploration. High-resolution seismic exploration for urban active fault calls for specific performance of the seismic source, because of peculiar environment in urban areas and particular characteristics of urban buried faults. For examples, relatively small offset of the fault requires a wider source spectrum, while strong disturbances in urban areas need a higher anti-jamming capability of the source. A comparative experiment on various types of sources, including vibroseis, vacuum accelerating weight drop, hammer-blow, air gun and explosive is carried out along the traverse across the Bayishuiku Fault. The features of various source spectrums are obtained by using spectrum analysis technique. The comparison of time-stacked sections obtained by using vibroseis, vacuum accelerating weight-drop and hammer blow from the traverse across the Bayishuiku Fault in Fuzhou City is presented in this paper. The effectiveness of various seismic sources in the exploration of urban buried active faults is discussed in detail.