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1.
This paper presents a summary of the seismicity and its relation to stress and geologic structures in the Eastern Great Lakes Basin (EGLB) and compares it with that of other regions in the central and eastern North America (CENA). The earthquakes scattered throughout the EGLB are occurring at a rate somewhat less than that of the Appalachians and along the Atlantic Seaboard. Paleoseismology studies suggest that the lower seismicity rate may be characteristic of the EGLB since the Late Wisconsin. North of the EGLB, earthquakes have primarily thrust mechanisms, while to the south of the EGLB, most earthquakes are strike-slip. Throughout the region, including the EGLB, the average P axes of the earthquakes are oriented NE–SW and are aligned with the direction of the current plate driving stress. On a regional basis, earthquakes are centered primarily in the Precambrian basement beneath the Paleozoic cover. Many of the earthquakes in the EGLB have occurred in areas of preexisting faults, at least some of which may have been active during past episodes of continental rifting. For individual faults that have been studied in some detail, however, it is not clear whether earthquakes represent reactivations of local preexisting structures or nucleation of new ruptures in or near the old fault zones. 相似文献
2.
鄂尔多斯块体新生代构造活动和动力学的讨论 总被引：54，自引：1，他引：53
鄂尔多斯块体除西南边界为挤压边界外,四周被共轭剪切拉张带所围限,东西和南北两侧分别为右旋和左旋剪切拉张带,全新世水平和垂直滑动速率分别达5mm/a和0.3~3mm/a。鄂尔多斯块体自始新世起从西南挤压边界两端开始发育,逐渐向远端发展,至上新世最后形成山西断陷盆地带。新生代以来块体不断缓慢上升,距今1.40Ma以来的隆起总量为160m.形变测量说明块体现代隆升速率为1~2.8mm/a,周缘断陷盆地带现代下降速率为-4~-5mm/a。块体内部莫霍面变化平缓,埋深40km~42km,上地幔高导层埋深123km~131km,它们在周缘断陷盆地带相对隆起,前者隆起幅度1.5km~6km,后者埋深仅70km~100km.6级以上地震均发生在块体周边活动构造带内,块体内部无6级以上地震发生,4~5级地震也很少。震源机制、地应力和断层滑动矢量测量等得到的主压应力方位为NE-NEE向,与控制块体周边活动构造的区域应力场一致,主要与青藏块体的NE向挤压作用相关,盆地地下深部物质上涌产生的垂直力也起着重要作用。所以,区域性水平应力场和深部物质运动产生的垂直力联合作用是本区新构造活动的动力条件。 相似文献
3.
中国活动构造与地震活动 总被引：56，自引：3，他引：56
文中研究了中国活动构造与地震活动的关系 ,包括活动断裂、活动褶皱、活动盆地和活动块体与地震活动的关系。全部 8级、绝大部分 7～ 7.9级地震均发生在活动块体边界活动构造带内 ;但对内部有次级活动构造的块体而言 ,少数 7～ 7.9级地震和部分 6～ 6 .9级地震也可能发生在块体内部的活动构造带上。大地震与活动断裂、活动褶皱和活动盆地的关系十分紧密 ,70多次 7级以上地震的同震破裂带及其位移参数与活动构造完全一致 ,7～ 8级地震均发生在活动断裂、活动褶皱和活动盆地带内 ,仅个别地震由于发生在高原和高山区 ,情况不明 ,6～ 6 .9级地震则大约有 5 %～ 15 %发生在活动构造带外或者情况不明。由于中国各断块区应力环境的差别 ,各区活动构造变形和地震发震构造类型也有所不同 ,文中对不同构造区走滑型 ,逆断裂褶皱型和正断裂拉张型活动构造和地震发震构造模型作了讨论。 相似文献
4.
We present data analysis of multi-electrode measurements performed in the tectonosphere-atmosphere interface at Pizzoli and Chieti observatories located at distances 30–50 km and 90–110 km from earthquakes epicenters in Central Italy accordingly. Time intervals include 30 days of observations before earthquakes occurred on 24 August (M6.2), on 26 October (M6.1) and on 30 October, 2016 (M6.6). The recorded signals are two component time series with time step 1 s representing alternative and direct electromotive force components. Alternative electromotive force component in frequency band of 0.01 Hz to 4000 Hz is being recorded. Basic study has been carried out since 1989 at Kamchatka peninsula and since 2012 across Eurasia. The observation of nonstationary electric processes illustrates the nucleation of seismogenetic activity. We propose the hypothesis that nonstationary (sudden, abrupt in amplitude) electrical signals illustrate the proton permeability of rocks laying underneath the measuring sensor including a unique phenomenon of anomalous spontaneous deformation due to combination of proton environment and polymorphic transformation in condensed media. One of the interesting results is distinguishing the main zone of major earthquake nucleation which is corresponding as the earthquakes epicenters in Central Italy with M > 6. We suggest that by covering the northern, central and southern parts of Italy with a network of multi-electrode observatories near fault lines, towns and villages could pinpoint the possible coordinates of earthquake epicenter in a 30 day time window. The Chieti and Pizzoli observatories can form the basis of an extended network. 相似文献
5.
Seismic coupling and uncoupling at subduction zones 总被引：1，自引：0，他引：1
Seismic coupling has been used as a qualitative measure of the “interaction” between the two plates at subduction zones. Kanamori (1971) introduced seismic coupling after noting that the characteristic size of earthquakes varies systematically for the northern Pacific subduction zones. A quantitative global comparison of many subduction zones reveals a strong correlation of earthquake size with two other variables: age of the subducting lithosphere and convergence rate. The largest earthquakes occur in zones with young lithosphere and fast convergence rates, while zones with old lithosphere and slow rates are relatively aseismic for large earthquakes. Results from a study of the rupture process of three great earthquakes indicate that maximum earthquake size is directly related to the asperity distribution on the fault plane (asperities are strong regions that resist the motion between the two plates). The zones with the largest earthquakes have very large asperities, while the zones with smaller earthquakes have small scattered asperities. This observation can be translated into a simple model of seismic coupling, where the horizontal compressive stress between the two plates is proportional to the ratio of the summed asperity area to the total area of the contact surface. While the variation in asperity size is used to establish a connection between earthquake size and tectonic stress, it also implies that plate age and rate affect the asperity distribution. Plate age and rate can control asperity distribution directly by use of the horizontal compressive stress associated with the “preferred trajectory” (i.e. the vertical and horizontal velocities of subducting slabs are determined by the plate age and convergence velocity). Indirect influences are many, including oceanic plate topography and the amount of subducted sediments.All subduction zones are apparently uncoupled below a depth of about 40 km, and we propose that the basalt to eclogite phase change in the down-going oceanic crust may be largely responsible. This phase change should start at a depth of 30–35 km, and could at least partially uncouple the plates by superplastic deformation throughout the oceanic crust during the phase change. 相似文献
6.
7.
Yuanzhong Lu Shuxin Yang Lianwang Chen Jianshe Lei 《Journal of Asian Earth Sciences》2011,40(4):990-1001
Strong earthquakes that occurred in the Chinese continent are usually characterized by grouped activity, long-distance jumping migration, and different main activity areas formed in different times. In the present study, a three-dimensional (3-D) finite element model was set up for the Chinese continent involving surface topography, major active fault zones and initial stress field to study the mechanism of the long-distance jumping migration of main active areas for the strong earthquakes that occurred in the Chinese continent. A number of numerical simulation experiments have been made by introducing the birth and death of element groups under different boundary loading configurations. Our results show that (1) in an environment where always exists an initial stress field in the Earth’s crust, the areas where strong earthquakes have occurred (taken as a killed element in the model) have no longer abilities to concentrate the stress largely enough and can cause the stress adjustment by an order of MPa in a large area, which may be one of the main factors affecting the long-distance jumping migration of the follow-up strong earthquakes, and (2) it is hard to accurately predict where the follow-up strong-earthquakes will occur because it could be affected by many factors such as the loading manner, geological structure, active fault zones, initial stress field, or stress field adjustment induced by strong earthquakes, but in an active period of earthquakes, the major activity area migration of strong earthquakes may be affected largely by the boundary loading configurations. These results suggest that it is helpful to predict a trend of the strong earthquake migration by investigating various kinds of boundary loading manners and the relationship between stress field adjustment induced by strong earthquakes and the regions where the strong earthquakes occurred. 相似文献
8.
中国东北地区地震空间分布与主要断裂带、深部构造及应力场关系 总被引：5，自引：1，他引：4
中国东北地区在北东东向应力场控制下, 地震有其特殊性。地震空间分布和深度统计结果表明, 东北地区地震主要受岩石圈断裂(开原-赤峰断裂带) 控制, 以44°N为界, 南北具有明显差异。北部地震发生的数量少于南部, 震源深度主要集中在4～6 km和8～12 km两个深度范围内; 而南部主要集中在8～12 km和28～30 km两个深度范围内。发震深度分析显示, 开原-赤峰、郯庐断裂带、大兴安岭断裂带下可能存在地温较低的区域, 使地震可以在深部孕育。地震分布的Vp和Vs剖面资料的研究暗示, 断裂与速度变化带、断裂与断裂的相交区域是地震易发生区域。 相似文献
9.
Characteristics of the seismicity in depth ranges 0–33 and 34–70 km before ten large and great (M
w
= 7.0−9.0) earthquakes of 2000–2008 in the Sumatra region are studied, as are those in the seismic gap zones where no large
earthquakes have occurred since at least 1935. Ring seismicity structures are revealed in both depth ranges. It is shown that
the epicenters of the main seismic events lie, as a rule, close to regions of overlap or in close proximity to “shallow” and
“deep” rings. Correlation dependences of ring sizes and threshold earthquakes magnitudes on energy of the main seismic event
in the ring seismicity regions are obtained. Identification of ring structures in the seismic gap zones (in the regions of
Central and South Sumatra) suggests active processes of large earthquake preparation proceed in the region. The probable magnitudes
of imminent seismic events are estimated from the data on the seismicity ring sizes. 相似文献
10.
根据卫星图像研究滇西滇中地区的断裂活动性，并结合水系分析，揭示东西赂主流水系与南北向、南东向非水流水系的分水岭以及金沙江、珠江水系的分水岭是重要的构造活动带。该区１０次７级以上地震，有８次发生在这些分水岭附近的活动断裂上。 相似文献
11.
The characteristics of the short-period shear wave attenuation field in the lithosphere of the Turanian Plate, West Tien Shan,
Pamir, and Hindu Kush have been studied. The method based on analysis of the logarithm of the ratio between maximal amplitudes
of Sn and Pn waves (Sn/Pn parameter) has been applied. More than 400 records of earthquakes, obtained at distances of ∼400–1000 km from the AAK digital
station, have been processed. It has been found that relatively weak attenuation is observed in the regions of the West Tien
Shan and Pamir. The largest area of strong attenuation is located in the region of the Afghan-Tadjik Depression adjacent to
Hindu Kush. A wide band of low Sn/Pn parameter values, stretched northeastwards, has been distinguished. Along with the analogous band of strong attenuation,
distinguished before in the regions of Central Tien Shan and Dzungaria, it is the continuation of the largest Chaman Fault,
which stretches 850 km along the boundary of the Indian Plate. Source zones of strong earthquakes with M ≥ 7.0 that occurred in the first half of 20th century correspond to relatively weak attenuation. Areas of high attenuation,
where strong seismic events have not occurred for the last 110 years, are outlined. Analogously to other seismoactive regions,
it is supposed that these areas are related to preparation of strong earthquakes. 相似文献
12.
It has been observed that the intensity of underwater gas flares unexpectedly increased after the deep-focus (625.9 km) earthquake that occurred in the Sea of Okhotsk on August 14, 2012. In this regard, we have analyzed the data resulting from interpretation of the focal mechanism for the strike-slip earthquakes which occurred in the Benioff seismic zone of the subducting Pacific Plate within the Sea of Okhotsk region over the period from 1977 to 2010. The NNW sinistral and NE dextral faults are found to form a conjugate system due to the WNW stress field. We have established that the dextral faults are mostly common at a depth of about 200 km along the Kuril Islands extension, while the sinistral ones are concentrated in the Nosappu Fracture Zone and traced to the NNW down to a depth of 680 km. The area of the gas flare discharge and gas hydrate accumulations have the same (NNW) direction. Thus, we have revealed that the Nosappu Fracture Zone appears to be a structure which controls fluid fluxes, providing permeability of the subducting slab of the Pacific Plate for ascending fluids from the lower mantle. 相似文献
13.
A temporary network of microearthquake seismographs deployed in the northern part of Svalbard recorded numerous earthquakes during the summer of 1982. Most of the earthquakes occurred in concentrated zones in restricted portions of three fault complexes in central Nordaustlandet, but minor activity also occurred to the east and west of these complexes. Within the uncertainty of the epicentral locations, most earthquakes which occurred on land in regions not covered by glaciers could be associated with segments of mapped faults. There are numerous fault segments and even entire faults, however, along which no recorded earthquake occurred. The concentrated spatial locations of these earthquakes along preferred portions of mapped faults, and the absence of throughgoing lines of activity, suggest that these are intraplate earthquakes occurring along existing faults in response to an applied stress field. Composite fault-plane solutions for the three most active regions each include one nodal-plane which can be associated, at least roughly, with a trend of seismicity and trend of a mapped fault. The directions of greatest principle stress for the three fault plane solutions vary between N90°W and N55°W, directions which agree approximately with maximum stress directions determined for a region about 200 km to the south. The consistency of the directions of maximum principle stress obtained for earthquakes throughout a broad region of Svalbard suggests that the earthquakes there occur in response to a stress field which is of plate tectonic origin. 相似文献
14.
What triggers Koyna region earthquakes? Preliminary results from seismic tomography digital array 总被引：1，自引：0，他引：1
S. S. Rai Sunil K. Singh P. V. S. S. Rajagopal Sarma D. Srinagesh K. N. S. Reddy K. S. Prakasam Y. Satyanarayana 《Journal of Earth System Science》1999,108(1):1-14
The cause for prolific seismicity in the Koyna region is a geological enigma. Attempts have been made to link occurrence of
these earthquakes with tectonic strain as well as the nearby reservoirs. With a view to providing reliable seismological database
for studying the earth structure and the earthquake process in the Koyna region, a state of the art digital seismic network
was deployed for twenty months during 1996–97. We present preliminary results from this experiment covering an area of 60
× 80 km2 with twenty seismic stations. Hypocentral locations of more than 400 earthquakes confined to 11×25 km2 reveal fragmentation in the seismicity pattern — a NE — SW segment has a dip towards NW at approximately 45°, whilst the
other two segments show a near vertical trend. These seismic segments have a close linkage with the Western Ghat escarpment
and the Warna fault. Ninety per cent of the seismicity is confined within the depth range of 3–10 km. The depth distribution
of earthquakes delimits the seismogenic zone with its base at 10 km indicating a transition from an unstable to stable frictional
sliding regime. The lack of shallow seismicity between 0 and 3 km indicates a mature fault system with well-developed gouge
zones, which inhibit shallow earthquake nucleation. Local earthquake travel time inversion for P- and S-waves show ≈ 2% higher
velocity in the seismogenic crust (0–10 km) beneath the epicentral tract relative to a lower velocity (2–3%) in the adjoining
region. The high P- and S-wave velocity in the seismogenic crust argues against the presence of high pressure fluid zones
and suggests its possible linkage with denser lithology. The zone of high velocity has been traced to deeper depths (≈ 70
km) through teleseismic tomography. The results reveal segmented and matured seismogenic fault systems in the Koyna region
where seismicity is possibly controlled by strain build up due to competent lithology in the seismic zone with a deep crustal
root. 相似文献
15.
The Himalayan fold-thrust belt has been visited by many disastrous earthquakes (magnitude > 6) time and again. This active collisional orogen bordering Indian subcontinent in the north remains a potential seismic threat of similar magnitude in the adjoining countries like India, Pakistan, Nepal, Bhutan and China. Though earthquake forecasting is riddled with all conjectures and still not a proven presumption, identifying likely source zones of such disastrous earthquakes would be an important contribution to seismic hazard assessment. In this study, we have worked out spatio-temporal clustering of earthquakes (Mb ?? 4.5; 1964?C2006) in the Himalayas. ??Point density?? spatial statistics has helped in detecting 22 spatial seismicity clusters. Earthquake catalog is then treated with a moving time-distance window technique (inter-event time 35 days and distance 100 ± 20 km) to bring out temporal clusters by recognizing several foreshock-main shock-aftershock (FMA) sequences. A total of 53 such temporal sequences identified in the process are confined within the 22 spatial clusters. Though each of these spatio-temporal clusters deserves in-depth analysis, we short-listed only eight such clusters that are dissected by active tectonic discontinuities like MBT/MCT for detail study. Spatio-temporal clusters have been used to constrain the potential source zones. These eight well-defined spatio-temporal clusters demonstrate recurrent moderate to large earthquakes. We assumed that the length of these clusters are indicating the possible maximum rupture lengths and thus empirically estimated the maximum possible magnitudes of eight clusters that can be generated from them (from west to east) as 8.0, 8.3, 8.2, 8.3, 8.2, 8.4, 8.0 and 7.7. Based on comparative study of the eight cluster zones contemplating with their temporal recurrences, historical seismic records, presence of intersecting faults and estimated magnitudes, we have guessed the possibility that Kangra, East Nepal, Garhwal and Kumaun?CWest Nepal clusters, in decreasing order of earthquake threat, are potential source zones for large earthquakes (??7.7 M) in future. 相似文献
16.
蛇纹石脱水与大洋俯冲带中源地震(70~300km)的关系 总被引：4，自引：2，他引：4
蛇纹石脱水致裂作用是诱发大洋俯冲带中源地震(70~300km)的一种重要成因机制,它与中等深度双地震带的形成有很密切的关系。双地震带在冷俯冲带中是一种常见现象,它由上下相距20~40km的两个平行地震层组成。上地震层位于俯冲洋壳中,可能是洋壳蓝片岩脱水形成榴辉岩的系列脱水反应诱发了地震;下地震层位于大洋俯冲地幔中,可能是部分交代的地幔橄榄岩脱水控制着中源地震的分布。蛇纹岩在高温高压条件下的变形实验证实蛇纹石在脱水过程中引起岩石弱化和脆性破裂,这已经得到了对蛇纹石脱水过程中岩石物理性质和变形后样品的显微构造等理论研究上的支持。在蛇纹石脱水过程中,产生的流体与固体残留物分离,形成了大量的I型(张性)微裂隙,最终导致岩石破裂和形成断层。根据叶蛇纹石脱水反应相图,理论上在大洋俯冲带中蛇纹石脱水位置会出现双层结构,但只有平行于俯冲板块顶层等温线的一支才可能脱水诱发地震,并对应于双地震带的下地震层。下地震层所处的位置具有低的vp/vs值,暗示岩石圈大洋地幔顶层发生了部分交代。但它的交代机制尚不清楚,可能是海水通过洋底转换断层和/或沿着在外海沟隆起中形成的断层渗入大洋地幔顶层,并发生了洋壳和大洋地幔交代。双地震带在120~200km深度合一以后,冷俯冲带中所发生的中源地震可能与蛇纹石脱水有关,在热俯冲带中更可能与“湿”榴辉岩脱水有关。 相似文献
17.
Seiichi Miura Narumi Takahashi Ayako Nakanishi Tetsuro Tsuru Shuichi Kodaira Yoshiyuki Kaneda 《Tectonophysics》2005,407(3-4):165-188
The Japan Trench subduction zone, located east of NE Japan, has regional variation in seismicity. Many large earthquakes occurred in the northern part of Japan Trench, but few in the southern part. Off Miyagi region is in the middle of the Japan Trench, where the large earthquakes (M > 7) with thrust mechanisms have occurred at an interval of about 40 years in two parts: inner trench slope and near land. A seismic experiment using 36 ocean bottom seismographs (OBS) and a 12,000 cu. in. airgun array was conducted to determine a detailed, 2D velocity structure in the forearc region off Miyagi. The depth to the Moho is 21 km, at 115 km from the trench axis, and becomes progressively deeper landward. The P-wave velocity of the mantle wedge is 7.9–8.1 km/s, which is typical velocity for uppermost mantle without large serpentinization. The dip angle of oceanic crust is increased from 5–6° near the trench axis to 23° 150 km landward from the trench axis. The P-wave velocity of the oceanic uppermost mantle is as small as 7.7 km/s. This low-velocity oceanic mantle seems to be caused by not a lateral anisotropy but some subduction process. By comparison with the seismicity off Miyagi, the subduction zone can be divided into four parts: 1) Seaward of the trench axis, the seismicity is low and normal fault-type earthquakes occur associated with the destruction of oceanic lithosphere. 2) Beneath the deformed zone landward of the trench axis, the plate boundary is characterized as a stable sliding fault plain. In case of earthquakes, this zone may be tsunamigenic. 3) Below forearc crust where P-wave velocity is almost 6 km/s and larger: this zone is the seismogenic zone below inner trench slope, which is a plate boundary between the forearc and oceanic crusts. 4) Below mantle wedge: the rupture zones of thrust large earthquakes near land (e.g. 1978 off Miyagi earthquake) are located beneath the mantle wedge. The depth of the rupture zones is 30–50 km below sea level. From the comparison, the rupture zones of large earthquakes off Miyagi are limited in two parts: plate boundary between the forearc and oceanic crusts and below mantle wedge. This limitation is a rare case for subduction zone. Although the seismogenic process beneath the mantle wedge is not fully clarified, our observation suggests the two possibilities: earthquake generation at the plate boundary overridden by the mantle wedge without serpentinization or that in the subducting slab. 相似文献
18.
In estimating the likelihood of an earthquake hazard for a seismically active region, information on the geometry of the potential
source is important in quantifying the seismic hazard. The damage from an earthquake varies spatially and is governed by the
fault geometry and lithology. As earthquake damage is amplified by guided seismic waves along fault zones, it is important
to delineate the disposition of the fault zones by precisely determined hypocentral parameters. We used the double difference
(DD) algorithm to relocate earthquakes in the Koyna-Warna seismic zone (KWSZ) region, with the P- and S-wave catalog data
from relative arrival time pairs constituting the input. A significant improvement in the hypocentral estimates was achieved,
with the epicentral errors <30 m and focal depth errors <75 m i.e. errors have been significantly reduced by an order of magnitude
from the parameters determined by HYPO71. The earthquake activity defines three different fault segments. The seismogenic volume is shallower in the south by 3 km,
with seismicity in the north extending to a depth of 11 km while in the south the deepest seismicity observed is at a depth
of 8 km. By resolving the structure of seismicity in greater detail, we address the salient issues related to the seismotectonics
of this region. 相似文献
19.
Usage of an early warning and information system Web-site for real-time seismicity in Iceland 总被引：1，自引：1，他引：0
Iceland has been subjected to destructive earthquakes and volcanic eruptions throughout history. Such events are often preceded
by changes in earthquake activity over varying timescales. Although most seismicity is confined to micro-earthquakes, large
earthquakes have occurred within populated regions. Following the most recent hazardous earthquakes in 2000, the Icelandic
Meteorological Office (IMO) developed an early warning and information system (EWIS) Web-site for viewing near-real-time seismicity
in Iceland. Here we assess Web-site usage data in relation to earthquake activity, as recorded by the South Iceland Lowland
(SIL) seismic network. Between March 2005 and May 2006 the SIL seismic network recorded 12,583 earthquakes. During this period,
the EWIS Web-site logged a daily median of 91 visits. The largest onshore event (M
L 4.2) struck 20 km from Reykjavík on 06 March 2006 and was followed by an immediate, upsurge in usage resulting in a total
of 1,173 unique visits to the Web-site. The greatest cluster of large (≥M
L 3) events occurred 300 km offshore from Reykjavík in May 2005. Within this swarm, 9 earthquakes ≥M
L 3 were detected on 11 May 2005, resulting in the release of a media bulletin by IMO. During the swarm, and following the
media bulletin, the EWIS Web-site logged 1,234 unique visits gradually throughout the day. In summary, the data reveal a spatial
and temporal relationship between Web-site usage and earthquake activity. The EWIS Web-site is accessed immediately after
the occurrence of a local earthquake, whereas distant, unfelt earthquakes generate gradual interest prompted by media bulletins
and, possibly, other contributing factors. We conclude that the Internet is a useful tool for displaying seismic information
in near-real-time, which has the capacity to help increase public awareness of natural hazards. 相似文献
20.
Betim Muço 《Natural Hazards》2014,71(1):135-150
Even though central Virginia is far from the nearest plate boundaries, the region is well-known for minor-to-moderate shocks, which have occurred frequently since at least the eighteenth century. Many of its people have experienced small earthquakes, while infrequent larger ones have caused damage. The largest destructive earthquake (magnitude 5.8) in this seismic zone was recorded in August 2011. Smaller earthquakes that cause little or no damage are felt each year or two. It is difficult to link the earthquakes of this zone to known small faults which are numerous, deeply buried and do not show up at the surface. The mean earthquake depth since 1960 is 6.7 km. On the other hand, central Virginia is a big collector and transporter of precipitation water, which flows to the Atlantic Ocean through the James River and its tributaries. There are about 2,000 abandoned mining sites in Virginia with underground openings that can facilitate the interception and conveyance of surface water. This paper presents evidence that seismic activity in certain zones can be associated clearly with the hydrological effects of abundant precipitation. Such effects can increase tectonic stress, which surpasses the marginal amount when an earthquake occurs. We analyze the cross-correlation between precipitation or water discharge in the rivers and earthquake occurrence in the central Virginia seismic zone. This correlation is examined both over a long-term span (57–92 years) and with regard to individual cases in which earthquakes have followed the occurrence of intense hydrological phenomena such as torrential rainfall or hurricanes. As we probe for a correlation between earthquake time series for central Virginia and the monthly precipitation series at hydrometeorological stations located in the zone, we observe that the best cross-correlation is obtained for a time period of 3 months. The same time period applies to certain historical earthquakes that were preceded by large amounts of precipitation. These results support the hydroseismicity hypothesis, which points to the role of water in the generation of intraplate seismicity. 相似文献