Before the Huoshan earthquake, significant anomalies were detected in both the gravity and lithospheric magnetic fields. To comprehensively analyze the variations in these fields and their underlying mechanisms before and after the Huoshan earthquake, we used mobile gravity data from 2010 to 2015 and mobile geomagnetic data from 2013 to 2014 in Anhui Province and surrounding regions. Our analysis focused on gravity field changes from two perspectives: (1)the spatial and temporal variations in the gravity field and(2)the time series of gravity point values across the seismogenic fault(Tudiling-Luoerling fault). Additionally, we corrected for diurnal variations and long-term trends in the geomagnetic field, allowing us to track changes in the three components of the lithospheric magnetic field—total intensity, magnetic inclination, and declination—before and after the earthquake. Using wavelet multi-scale decomposition, we calculated and analyzed wavelet details at different decomposition scales for the gravity and magnetic field variations in the first half year before the Huoshan earthquake. Finally, in conjunction with underground fluid data, we examined the seismogenic background and explored the underlying reasons for the precursory anomalies observed in the geophysical fields.

The research yielded the following conclusions: Prior to the Huoshan earthquake, an anomalous high-gradient zone in both the gravity field and the total strength of the lithospheric magnetic field was observed, extending approximately 100km. Notably, the total magnetic field strength in the Huoshan area significantly decreased before the earthquake. The gravity field exhibited a small initial decline, evolving into a high-gradient anomaly zone parallel to the seismogenic fault, which culminated in the earthquake occurring near the zero contour of gravity change. The alignment of the zero lines of gravity and magnetic field changes with the strike of the seismogenic fault suggests that tectonic faults play a critical role in controlling crustal deformation and underground fluid migration. When combined with a comprehensive analysis of the regional stress field, underground fluid dynamics, and variations in the gravity and magnetic fields, this information can be instrumental in identifying and assessing seismic risk zones.

The Huoshan region is highly susceptible to seismic activity due to the influence of the Bayan Har block in the Qinghai-Tibet region, which induces stress field fluctuations in the area. The M_S7.0 Lushan earthquake in Sichuan, on April 20, 2013, significantly impacted the regional stress field, resulting in the opening of the “Huoshan Seismic Window.” In the six months preceding the Huoshan earthquake, there was an increase in crustal movement, as well as a marked rise in minor seismic activity. These factors accelerated the adjustment of the regional stress state and the migration of underground fluids, leading to expanded variations in regional gravity and magnetic fields. The Huoshan M_S4.3 earthquake exhibited distinct precursory anomalies. The wavelet multi-scale decomposition of gravity and magnetic field changes suggests that the source of the Huoshan earthquake likely originated in the middle to lower crust. The deformation and material migration in the upper crust appeared to be influenced by processes in the middle and lower crust, with energy accumulation in the upper crust triggering the opening of the “Huoshan Seismic Window” and the subsequent earthquake. Additionally, the extreme point of the wavelet details in the lithospheric magnetic field change was located near the zero line of the wavelet details in the gravity field and the fault development area.

This study concludes that regional stress fluctuations, crustal deformation, and underground fluid migration are controlled by fracture structures. The migration of underground fluids and other materials results in notable changes in the gravity and magnetic fields, particularly in areas with concentrated fault activity, underscoring the potential for predicting earthquakes using geophysical precursor signals such as gravity and lithospheric magnetic field changes.

The seismic activity in Dongtai, Jiangsu, suddenly intensified from November to December 2022. The largest earthquake observed during this period was a magnitude M_S3.0 event on 25 December, which was felt reported by many nearby residents and caused a certain degree of social impact. The Dongtai area is situated in the central part of Jiangsu Province, within the Dongtai depression in structure, which is a secondary tectonic unit in the southern part of the Subei-South Yellow Sea Basin. Multiple fault zones developed in the region. The prominent known fault zones near the epicenter include the Taizhou fault, the Chenjiabao-Xiaohai Fault, and the Benchahe Fault. Among them, the closest to the epicentral area is the Taizhou fault. Additionally, the Subei Basin has a long history of industrial activity. Its geological conditions are complex, and the resources are extremely scattered and fragmented. The scale of underground resource extraction is predominantly small to medium-sized and has entered the middle to high exploration level. Historically, Dongtai has experienced weak seismic activity with only six earthquakes of M_S≥3 within 50 kilometers of the epicenter since 1970. The sudden increase in seismic activity prompts investigation into its cause. Analyzing the structural features of the Dongtai earthquake sequence can enhance understanding of seismic activity and seismogenic mechanisms in the region.

Previous studies on regional velocity structure have primarily focused on large scales, such as the Tan-Lu fault zone, with no specific research dedicated to the Dongtai earthquake sequence. In this study, we collected earthquake arrival time data recorded by the China Earthquake Networks Center from 2008 to 2022. Employing the double-difference tomography method, we conducted a joint inversion to investigate the velocity structure and earthquake locations in the Subei Basin. The resulting outcomes include the three-dimensional P-wave velocity structure of the area and the relocation results of 22 events within the seismic sequence. Furthermore, utilizing clear P-wave initial motion data from station waveform records, we inverted the focal mechanism solutions of the earthquake sequence using a modified grid search method. By integrating these inversion results with data on fault distribution and local industrial activity, we discussed the earthquake-triggering mechanism and possible seismogenic structures.

The results indicate that: 1)Following relocation, the seismic sequence exhibits a zonal distribution pattern. The earthquakes are predominantly situated north of the Tai-Zhou fault in a nearly north-south orientation, spanning approximately 15 kilometers in total length, with a predominant depth range of 11 to 16 kilometers. Notably, there is no apparent correlation between the earthquakes and the surrounding known fault structures. 2)The focal mechanism solution parameters for the largest earthquake in the sequence, M_S3.0, suggest a strike-slip seismogenic structure with a minor normal component. The direction of the stress axis aligns closely with the current tectonic stress field of the study area. Based on the focal mechanism solution and the distribution of the sequence, it is inferred that a dextral strike-slip hidden structure trending in a NNE-SSW direction may exist beneath the sequence. 3)The velocity structure of the epicenter area exhibits significant heterogeneity. The middle crust displays relatively high velocity, while the lower crust shows relatively low velocity. Notably, a spindle-shaped high-velocity anomaly with a P-wave velocity of 6.25km/s is observed at a depth of approximately 15km. The earthquakes primarily cluster southeast of this anomaly. 4)By examining the relationship between the spatial locations of earthquakes and their occurrence times, it is observed that the epicenters exhibit a seismogenic process extending far from the edge of the anomalous body. This suggests the outward release of accumulated elastic energy within the high-velocity anomaly, indicating a potential relationship between earthquake occurrences and the velocity anomaly. 5)Through on-site investigations of the epicentral area, data regarding local industrial activities have been collected. It was observed that three new wells and multiple industrial operation points have been established in the seismic area. Remarkably, 73% of earthquakes in the seismic sequence occurred within a 4.6km radius of well H1, with the largest earthquake in magnitude located approximately 1km from the well. A notable correspondence is observed between the Wulie-Shiyan-Qindong extraction points, the seismic sequence, and the deep high-velocity anomaly. Additionally, the operational timeframe of newly developed wells in the region closely aligns with the timing of earthquakes. However, the dominant depth of seismicity does not correspond with the drilling depth. A preliminary inference suggests that the occurrence of the earthquake sequence may be linked to the deep heterogeneous velocity structure, while industrial production activities near the epicenters may induce alterations in the regional stress state, leading to stress destabilization and subsequent energy release.

Bouguer gravity anomaly is a comprehensive reflection of deep and shallow density disturbances of the Earth’s internal mass. Important tectonic information of internal structure at different depths can be obtained by source separation of Bouguer gravity anomaly. Bouguer gravity anomaly from ground-based observations and Bouguer gravity anomaly from EGM2008 of the eastern Dabie Orogen were merged based on least-squares collocation. By model construction of massive bodies and data experiments, optimal wavelet base(sym6)and the corresponding optimal level(6)for gravity anomaly decomposition of the study area were confirmed. Two-dimensional discrete wavelet transform method was applied to obtain low-frequency components and high-frequency components of merged Bouguer gravity anomaly of the study area, and average depths of disturbed surfaces of the wavelet decomposition results were determined by spectrum analyses. In combination with data of crustal structure, geologic structure, effective elastic thickness of lithosphere and seismic activities, the deep structure and shallow structure of the crust were analyzed, and the structural background of seismic activities was discussed. The result shows that steep gradient belts of low-frequency components of Bouguer gravity anomaly outline the density transfer zones of deep structure between the eastern Dabie Orogen and surrounding blocks. It is speculated that the suture zone between the eastern Dabie Orogen and the North China Block locates at the front edge of Qingshan-Xiaotian Fault(the eastern part)and Meishan-Longhekou Fault(the western part), the structure transfer zone between the Dabie Orogen and the Yangtze Block locates at the Tancheng-Lujiang fault zone(the eastern part)and 20km north of Xiangfan-Guangji Fault(the southern part). The interior of the eastern Dabie Orogen is characterized by significant low gravity anomaly, which means an obvious depression of Moho surface, and the steep gradient belts of gravity anomaly inside the eastern Dabie Orogen indicate the imperfection of deep structure. High-frequency components of Bouguer gravity anomaly reveal that density structure of the mid-upper crust was influenced by regional faults such as Feizhong Falut, Lu’an-Hefei Fault, Meishan-Longhekou Fault and Tancheng-Lujiang fault zone. The distribution of high-frequency Bouguer gravity anomaly shows that Luo’erling-Tudiling Fault has obvious effect on density structure of the mid-upper crust, and the range of influence breaks northward through the NWW-orientated Qingshan-Xiaotian Fault and Meishan-Longhekou Fault, and may extend to the front edge of Feixi-Hanbaidu Fault. Further analysis combined with seismic activities shows that plate contaction occurred along the suture zones(front edge of Qingshan-Xiaotian Fault)of deep structure between the eastern Dabie Orogen and the North China Block. Besides, deep and shallow structures of this area are both imperfect, and not strong enough for long-time stress accumulation. Therefore, rocks tend to break at weak points(locations where faults intersect and shallow structure transfers)and release stress frequently, which are main reasons why small earthquakes concentrated at Huoshan area.

A strong earthquake with magnitude M_W=7.1 occurred in the area of Molucca Sea, Indonesia on November 14, 2019(Coordinated Universal Time, UTC), and then generated a small-scale local tsunami. In order to better understand the earthquake source characteristics and seismogenic structure, as well as to assess the hazard of tsunami caused by earthquake, this paper mainly focuses on the regional tectonic background, the focal mechanism, and tsunami numerical simulation for the Molucca Sea M_W7.1 earthquake. The broadband seismic waveforms from IRIS Data Management Center are used to estimate the moment tensor solution of this earthquake by W phase method. The result shows that the Molucca Sea earthquake occurred at a shallow depth on a high dip-angle, right-lateral reverse fault, the aftershocks were distributed along the SSW-NNE direction and concentrated near the main shock. These results indicate the Molucca Sea earthquake with characteristic of compressional rupture occurred in the complex plate boundary region of eastern Indonesia, which is dominated mostly by the collision interaction of the Halmahera slab and the Sangihe slab in the east and west sides of Molucca Sea under control of current regional stress field. The coseismic displacements of Molucca Sea M_W7.1 earthquake calculated using Okada's model of rectangular dislocation in a uniform elastic half-space show that the Molucca Sea earthquake generated vertical coseismic deformation with a maximum uplift of 0.15m when the rupture occurred along the high dip-angle reverse fault. The synthetic tsunami waveforms are provided by COMCOT tsunami modelling package solving the nonlinear shallow water wave equations based on the determined fault geometry from W phase inversion. These studies indicate the vertical coseismic deformation resulting in the sudden uplift of water volume above the earthquake source, and finally inducing a small-scale local tsunami. The energy of tsunami mainly propagates to both side of the fault, and part of energy propagates to Sula Islands of Indonesia along the fault dislocation direction; and compared with the first cycle of tsunami records observed by tide gauges deployed along the coastal line of earthquake source region, the observed tsunami head wave fits well with the synthetic wave, both are consistent in amplitude and tsunami arrival time, but the follow-up waveforms are quite different. The numerical simulation of tsunami shows that, in combination with the fault geometry parameters obtained by W phase fast inversion, the tsunami numerical model can be used for tsunami early warning, and it provides sufficient accuracy for forecasting tsunami wave height, thus, having great practical significance for understanding the propagation process and disaster distribution of tsunami.

The middle-southern segment of the Tan-Lu fault zone and its adjacent area is located in the joint zone of the North China craton and Yangtze craton. It is a natural test ground for studying the problems of intracontinental collision, continental convergence and growth, geodynamics and lithospheric deformation. Although early research involved the central-south section of the Tan-Lu fault zone and its neighboring areas, it is difficult to carry out a detailed discussion on the S-wave velocity and azimuthal anisotropy in the middle and south section of the Tan-Lu fault zone and its adjacent areas, due to different research purposes and objects, the limitation in selecting research scope or the lack of resolution.
To obtain more detailed crust-mantle velocity structure and azimuthal anisotropy distribution characteristics in the study area, this paper uses waveform data recorded by 261 fixed wideband seismic stations in the middle-southern segment of the Tan-Lu fault zone and its adjacent zone for two consecutive years. The phase velocity dispersion curve of Rayleigh surface wave with 5~50s period was extracted by time-frequency analysis. Then, the study area was divided into 0.25°×0.25°grids, and the two-dimensional Rayleigh phase velocity and azimuthal anisotropy distribution image in the area was retrieved using the Tarantola method.
The phase velocity and azimuthal anisotropy distribution images of 6 representative periods were analyzed. These images reveal the lateral heterogeneity of the crust-mantle velocity structure and spatial differences in azimuthal anisotropy in the middle-southern segment of the Tan-Lu Fault and its adjacent areas. The results show that the distribution characteristics of phase velocity have a good correspondence with geological tectonic units. In the shallow part of the earth's crust, the basins covered by thick unconsolidated sedimentary layers and the bedrock exposed orogenic belts show low and high velocity anomalies, respectively. With the increase of the period(15~20s), the influence of the shallow sedimentary layer is weakened, and the high-speed anomaly appears in some plain areas such as the Hehuai Basin and Subei Basin. The distribution of phase velocity in the lower crust and upper mantle(25~30s)is affected by the thickness of the crust, which is inversely related to the burial depth of Moho surface. For example, the Dabie orogenic belt with a thickness of 40km changes from a short period high-speed to a low-speed distribution.
Due to the differences in the tectonic environment of each geological structural unit in the study area, the azimuthal anisotropy of Rayleigh waves has obvious spatial differences. In general, the strength of anisotropy increases with increasing period(depth), and the direction of fast wave is more regular and followable. Based on the consistent distribution of low velocity and azimuthal anisotropy from the shallow crust to the lithospheric mantle in the Subei Basin, we believe that there may be a strong crust-mantle coupling phenomenon. The results obtained by different seismic anisotropy observation methods are different manifestations of anisotropy. However, due to the one-sided and low-resolution problems of single observation method, it is necessary to carry out joint inversion or comprehensive multiple observation methods.

The seismogenic structure of the Lushan earthquake has remained in suspensed until now. Several faults or tectonics, including basal slipping zone, unknown blind thrust fault and piedmont buried fault, etc, are all considered as the possible seismogenic structure. This paper tries to make some new insights into this unsolved problem. Firstly, based on the data collected from the dynamic seismic stations located on the southern segment of the Longmenshan fault deployed by the Institute of Earthquake Science from 2008 to 2009 and the result of the aftershock relocation and the location of the known faults on the surface, we analyze and interpret the deep structures. Secondly, based on the terrace deformation across the main earthquake zone obtained from the dirrerential GPS meaturement of topography along the Qingyijiang River, combining with the geological interpretation of the high resolution remote sensing image and the regional geological data, we analyze the surface tectonic deformation. Furthermore, we combined the data of the deep structure and the surface deformation above to construct tectonic deformation model and research the seismogenic structure of the Lushan earthquake. Preliminarily, we think that the deformation model of the Lushan earthquake is different from that of the northern thrust segment ruptured in the Wenchuan earthquake due to the dip angle of the fault plane. On the southern segment, the main deformation is the compression of the footwall due to the nearly vertical fault plane of the frontal fault, and the new active thrust faults formed in the footwall. While on the northern segment, the main deformation is the thrusting of the hanging wall due to the less steep fault plane of the central fault. An active anticline formed on the hanging wall of the new active thrust fault, and the terrace surface on this anticline have deformed evidently since the Quaterary, and the latest activity of this anticline caused the Lushan earthquake, so the newly formed active thrust fault is probably the seismogenic structure of the Lushan earthquake. Huge displacement or tectonic deformation has been accumulated on the fault segment curved towards southeast from the Daxi country to the Taiping town during a long time, and the release of the strain and the tectonic movement all concentrate on this fault segment. The Lushan earthquake is just one event during the whole process of tectonic evolution, and the newly formed active thrust faults in the footwall may still cause similar earthquake in the future.

The relationship between the latest displacement of active fault and seismic events is an important basic problem. Taking the Sihong segment of the Tan-Lu Fault as the main research area, we selected the Chonggangshan-Wangqian segment as the study section by Google map terrain analysis, excavated 6 large scale trenches, identified and cataloged the Late Quaternary deformation events and prehistoric earthquake relics, analyzed activity stages and behavior of the section. The result indicates that the Chonggangshan-Wangqian segment of the Tan-Lu Fault has undergone intense compression and thrust movement since the Late Quaternary. It is displayed that the brick-red sandstone of Upper Cretaceous thrust at high angle over the yellowish-brown clay of the Late Pleistocene in Chonggangshan segment, while the white or yellow sandstone of Oligocene in Wangqian segment thrust westward over the Late Quaternary sediments, accompanied by rifting activity. By the ¹⁴C dating, we get two paleoearthquake events, and their age is (11 755±45)～(10 525±45)a BP and about(10 135± 50)a BP, respectively. This suggests that the Chonggangshan-Wangqian segment of Tan-Lu Fault zone has undergone strong thrust movement since the late Pleistocene, and this activity had continued to the early Holocene.

From the teleseismic P-waveform data recorded at the dense mega seismic array deployed in the western Sichuan area by the State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,we investigate the crustal anisotropy beneath the stations using waveform correlation method and weighted stacking method. As a preliminary result,we measured the fast polarization azimuth and time delay of the Ps converted wave in the receiver functions at 4 stations on both sides of Longmen Shan Faults. Our results show:1)The waveform correlation method is better than the weighted stacking method and it turns out not only the fast polarization azimuth,but also the time differences between the fast-and slow-wave; The results obtained by using the weighted stacking method are something undetermined due to that the symmetric axis of the crustal anisotropy medium is unclear previously; Application of both methods will be in favor of judging the reliability of the results. 2)The fast polarization azimuths are consistent each other at the stations in Sichuan Basin,suggesting the crust beneath Sichuan Basin has well integrality and a weak lateral deformation. 3)Taking the epicenter of the Wenchuan earthquake as a boundary,the fast polarization azimuth is parallel with the Longmen Shan Faults on the north side of the Sonpan-Ganzi block,and perpendicular to the faults on the south side. This suggests that under the obstruction of the Sichuan Basin,the soft lower crust beneath the north side of the Sonpan-Ganzi block has a NE direction extended deformation along the Longmen Shan Faults,and the crust on its south side is in the status of compressive deformation perpendicular to the faults. Our results can be used for interpreting the single-side rupture of the Wenchuan earthquake and the aftershock evolution.

In the western Sichuan(100°～105°E,26°～32°N),a mobile array consisting of 297 broadband seismic stations has been deployed by the State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration since October of 2006.Until June of 2008,a total of 690 teleseismic events(m_b>5.0,30°≤Δ≤90°)have been recorded.The May 12 Wenchuan earthquake(M_S8.0)provides an opportunity to test the western Sichuan array.The preliminary data analysis of the May 12 Wenchuan earthquake and its larger aftershocks has been carried out in this study.Our results show: 1)The event parameters of the May 12 Wenchuan earthquake sequence need to be modified and their location error reaches to 8～24km.A more reasonable estimation of the location of the main shock is possibly at the depth of 19km.2)the wavefield analysis of the Lixian earthquake(M_S5.9)of May 16,2008 manifests that the surface waves of this event are not fully developed,and thus its source depth should not be very shallow.The peak values of the ground-motion velocity on the vertical and horizontal component have an abnormal increase by 4 times and more of the normal attenuation,which is related closely to the faults within the range of 200～250km,when the topography and site effects are not considered.3)The preliminary analysis of the crustal and upper mantle structure beneath the Sichuan basin and the Songpan-Ganzi block manifests that the crust beneath the Sichuan basin thickens along the western direction and its lower crust displays the hard structure.The crustal thickness in the northeast of Chengdu City reaches 46km.The crustal structure beneath the Songpan-Ganzi block has complex lateral variations.The crustal thickness in the Wenchuan earthquake source region reaches 52km.In the depth range of 14～20km,its crust has a complex high-velocity structure with the averaged velocity larger than 4.0km/s.The Wenchuan earthquake should be located within the area with high-velocity medium.In the lower middle crust,a low-velocity layer exists with the S-wave velocity of～3.6km/s,which could provide a relaxed boundary condition for the upper crust movement-deformation.This observation is consistent with the abnormal attenuation of ground motion with the epicenter distance obtained from the wavefield measurements.

The thinking of earthquake research in China should be shifted from the viewpoint of fault to active block (MA Jin, 1999). ZHANG Pei-zhen et al. divide the active blocks in Chinese mainland and its adjacent area into two degrees: the first degree refers to active-block regions and the second degree refers to active blocks. The former contains 6 block regions, e.g. the Qingzang (Qinghai-Tibet) region, etc. and the latter contains more than 20 active blocks, e.g. the Lhasa block and so on. We attempt to analyze the characteristics of geological structure and focal mechanism of group strong earthquakes that occurred recently in Chinese mainland from the block viewpoint on the basis of the two-degree active blocks. The strong earthquakes (M≥7 in the west and M≥6 in the east) occurring in China of 1977—2003 can be roughly divided into 9 groups. In summary, the strong earthquakes occurring in the recent 10 years still have the grouping feature and most of them are located in the boundary zones between active-block regions or active blocks. Moreover, their focalmechanism solutions are quite similar to each other, except for the earthquakes in the 4th group (the earthquakes that occurred in the Beibu Gulf and the Taiwan Straits can be considered as an individual case) and in the 5th group (the earthquakes that occurred in Mandalay-Diannan block near the plate boundary are not regarded as intraplate earthquakes). Based on the study of horizontal strain field in Chinese mainland and its surroundings with GPS data, we point out in the paper that group strong earthquakes have their own genesis for the similar motion pattern and dynamic origin. From the above analysis, we conclude: (1) The rule of strong earthquake occurrences in groups is still effective after more than 10 years practice, and it is an applicable method for locating earthquakes in the medium and short-term earthquake predictions. (2) The regional characteristics of group strong earthquakes enable us to predict the location of earthquakes in a smaller range on the boundary zone between the second-degree blocks in a first-degree block region or between two first-degree block regions. (3) Except plate-margin area, the group strong earthquakes have consistent focalmechanism solutions. This indicates that they have similar kinetic mechanisms and dynamic processes, or perhaps, we can say, that they develop monolithically and occur successively.

The 1830 Cixian, Hebei province, M 7(1/2) earthquake is a strong sequence with high activity and long duration In recent years, a large amount of small shocks have been recorded in the region of Cixian county by the Handan remote sensing seismological network The 3 dimensional spatial distribution of focuses and focal mechanism of these small shocks are analyzed It is suggested that the focal fault of the 1830 Cixain earthquake is a fault with NWW strike and left lateral strike slip This result is in agreement with the isoseismal and surface rupture belt of the Cixain earthquake Therefore, it is feasible to outline spatial orientation and motion mode of the focal fault of historical great earthquakes from characteristics of swarms of current small shocks which occurred in the historical seismic region by combining method of seismology and geology

The study area,an old continent block with a Coledoman folding basement,is located 20-31.5°N,115-122°E,along the southeastern edge of the Eurasian plate.Granite and volcanic rocks are widespread throughout this area with an age decreasing from west to east.The Yanshanian granite exists mainly along the coast and the tectonic activity also shows an increase to the coast.For the coastal area the geothermal gradient and the geotemperature show a higher value ranging from 50-70℃ at a depth of 1000m and 2000m,respectively,and the highest up to 60℃ and 90℃,somtimes even to 100℃and 130℃.Presented here are some data from the Wuyi Mountains,the Moyang Basin and the Jinqu Basin and the like.Distributions and formation of the geothermal field are dependent on deep structures in the earth's crust and the regional geotemperature,on the crustal thickness as well as on the geological structures.The occurrence and distribution of the hot springs are correlated with two major deep faults striking NE and NW.In addition the content of radioactive elements in the Yanshenian granite is about two times higher than that of the contemporaneous granite found in North China.Two types of geothermal field may be distinguished in the study area:1) conduction and 2) conduction superposed by hot water conduction.