Reservoir Earthquakes Research Articles

Machine learning-based automatic construction of earthquake catalog for reservoir areas in multiple river basins of Guizhou province, China

Large reservoirs have the risk of reservoir induced seismicity. Accurately detecting and locating microseismic events are crucial when studying reservoir earthquakes. Automatic earthquake monitoring in reservoir areas is one of the effective measures for earthquake disaster prevention and mitigation. In this study, we first applied the automatic location workflow (named LOC-FLOW) to process 14-day continuous waveform data from several reservoir areas in different river basins of Guizhou province. Compared with the manual seismic catalog, the recall rate of seismic event detection using the workflow was 83.9%. Of the detected earthquakes, 88.9% had an onset time difference below 1 s, 81.8% has a deviation in epicenter location within 5 km, and 77.8% had a focal depth difference of less than 5 km, indicating that the workflow has good generalization capacity in reservoir areas. We further applied the workflow to retrospectively process continuous waveform data recorded from 2020 to the first half of 2021 in reservoir areas in multiple river basins of western Guizhou province and identified five times the number of seismic events obtained through manual processing. Compared with manual processing of seismic catalog, the completeness magnitude had decreased from 1.3 to 0.8, and a b-value of 1.25 was calculated for seismicity in western Guizhou province, consistent with the b-values obtained for the reservoir area in previous studies. Our results show that seismicity levels were relatively low around large reservoirs that were impounded over 15 years ago, and there is no significant correlation between the seismicity in these areas and reservoir impoundment. Seismicity patterns were notably different around two large reservoirs that were only impounded about 12 years ago, which may be explained by differences in reservoir storage capacity, the geologic and tectonic settings, hydrogeological characteristics, and active fault the reservoir areas. Prominent seismicity persisted around two large reservoirs that have been impounded for less than 10 years. These events were clustered and had relatively shallow focal depths. The impoundment of the Jiayan Reservoir had not officially begun during this study period, but earthquake location results suggested a high seismicity level in this reservoir area. Therefore, any seismicity in this reservoir area after the official impoundment deserves special attention.

Preface to the special issue on ground motion input at dam sites and reservoir earthquakes

Preface to the special issue on ground motion input at dam sites and reservoir earthquakes

Influence of Three Gorges Dam on earthquakes based on GRACE gravity field

Abstract After the completion of the Three Gorges Dam, it increases the risk of inducing an earthquake. We use the GRACE Gravity Field Model to analyze the relationship between the operation of the Three Gorges Reservoir and the change of gravity field in western Sichuan. The research results indicate that the reservoir water level and the western Sichuan gravitational field are positively correlated. In the early stage of rising water level, the change of gravity field is not apparent, and the change of gravity field gradually increases with time. Therefore, the change of reservoir water level affects the gravity field in western Sichuan. The dynamic changes of the gravity field can reflect the Earth’s material change and deformation process and are closely related to earthquakes. Consequently, the Three Gorges Dam will indirectly affect the seismicity in western Sichuan by affecting the gravity field. The research provides valuable information for studying regional reservoir earthquake disasters and supports related policy decisions.

Analysis of Reservoir Seismic Law Based on Three-Dimensional Morphological Characteristics of Joint Surface Related to Listric Fault

Since water storage, earthquakes occurred in Badong County, Hubei Province, accounted for as much as one-third of the strong earthquakes in the Three Gorges Reservoir area. For example, the MS5.1 earthquake occurred in December 2013 near the Gaoqiao fault in Badong County. The earthquake time, magnitude, and location analysis showed that reservoir earthquakes in this area exhibited some characteristics, such as periodicity, migration, and deep extension. Based on the regional stratum lithology and structural characteristics, this paper designed a curved joint on a small scale to simulate the structural morphology of the Gaoqiao fault and carried out triaxial compression tests under different immersion times to analyze the morphological parameters of the joint surface. The results showed that topological parameters such as root mean square height (Sq), arithmetic average height (Sa), reverse load area ratio (Smc), and minimum autocorrelation length (Sal) could effectively characterize the degree of damage and deterioration of curved joints. The test privides a reference for analyzing the evolution law of the seismic characteristics of the reservoir.

Study on moderate earthquake risk of the Xinfengjiang reservoir from 3D P-wave velocity structure and current seismicity parameters

In this paper, we determined the Xingfengjiang Reservoir earthquake sequence location from June 2007 to July 2014 and 3D P-wave velocity structure by a simultaneous inversion method. On that basis, we mapped the b-value 3D distribution. The results show the low b-value distribution consists with the high velocity zone(HVZ) and most earthquakes occurred around the HVZ. Under the reservoir dam there is a strong tectonic deformation zone, as the centre exit Renzishi fault F2, Nanshan - Aotou faults F4, Heyuan fault F1 and Shijiao-xingang-baitian fault F5. M6.1 Xinfengjiang earthquake, 19 Mar 1962, occurred in the strong tectonic deformation zone, and now the zone b≥0.7, so a short period of the original earthquake occur more unlikely. The b-value of the HVZ under Xichang(in the northwest corner of XFJ Reservoir) ranges between 0.4 to 0.7 suggesting the rate of stress accumulations is greater than the speed of seismic energy release since 2012. We don’t exclude the possibility that the HVZ becomes the seismogenic asperity, and will occur M≥5 earthquake.

The Research of Reservoir Earthquake Prediction Based on the Design of Horizontal Well of Thin Carbonate Reservoir of J2 Gas Reservoir in Lingyinsi Structure

Compared to clastic rocks, the exploration and development of thin carbonate reservoir are 1more complex. Especially, the thin reservoir demands high resolution of seismic data. So the conventional methods are difficult to good exploration at the present time. According to the complexity of thin carbonate reservoir, we comprehensively analyze reservoir geology, logging and seismic response, combine natural gamma inversion, velocity inversion with porosity inversion for prediction of reservoir and obtain precise quantitative earthquake prediction. The analysis demonstrates the reliability of seismic reservoir prediction applied to design for horizontal well. On the basis of understanding the basic geological characteristics of the reservoir, this thesis takes the design for horizontal well of J21 for example, completes two sets of designs for horizontal wells group by combining prediction technology for reservoir seismic with geologic steering technique and greatly improve the drilling rate for thin reservoir.

High-Resolution Numerical Analysis of the Triggering Mechanism of M L5.7 Aswan Reservoir Earthquake Through Fully Coupled Poroelastic Finite Element Modeling

In 1981, a powerful M L5.7 earthquake occurred 50 km away from the Aswan Reservoir dam. After the statistical analysis on the correlationship between long-term continuous seismicity occurrence and the reservoir water level variation attributed to the impoundment and drainage procedures, researchers believe that this event is a typical reservoir-triggered seismicity (Nature 301(6):14, 1983; Earthquake Activity in the Aswan Region, Egypt. Birkhauser, Basel, pp. 69–86, 1995), although its triggering mechanism is poorly understood to date. To quantitatively address the triggering mechanism as well as its relationship with the characteristics of local geological settings around the reservoir region, in this paper, a fully coupled three-dimensional poroelastic finite element model of the Aswan reservoir is put forward by taking the consideration of the realistic observation data, for example, the high-resolution topography, water level fluctuation history, flood zone boundary and water depth variation, fault parameters, etc. Meanwhile, the change of Coulomb Failure Stress (ΔCFS) in correspondence to elastic stress and pore pressure variations induced by fluid diffusion is calculated. And the elastic strain energy accumulation in the reservoir region due to the impoundment load is obtained as well. Our primary results indicate that both the pore pressure and the coulomb stress on the seismogenic fault plane gradually increase with the respect of time while the water level rises. The magnitude of ΔCFS at the hypocenter of this major event is around 0.1 MPa, suggesting that the impoundment of the Aswan Reservoir possibly triggered the M L5.7 earthquake. The contribution of the elastic load is less than 3 percent of the total ΔCFS; on the other hand, the dynamic pore pressure change predominantly accounts for the contribution. The accumulative maximum surface deformation beneath the Aswan reservoir is up to 80 cm since its impounding began until the M L5.7 earthquake occurred. Although the total elastic strain energy accumulation caused by the impoundment water load is around 1.0 × 1010J, this energy density still insignificant compared to that of the vast reservoir inundation area, as it is only less than few percent of the total energy released by the major event, which confirms that the sustained regional geological loading controls the occurrence of this large reservoir-induced event. Furthermore, elastic loading and pore fluid pore pressure diffusion due to the impoundment of the Aswan reservoir might accelerate its occurrence.

Effect of Abutment Load of Arch Dam on Stability of Underground Caverns Complex

Considering topographic and geologic conditions, project layout and investments, concret arch dam is adopted in a hydropower plant and underground powerhouses are arranged in mountains on left and right banks. However, the minimum distance between the excavation boundary of abutment of arch dam on elevation 850m and underground powerhouse is only 110m. Abutment load created by reservoir storage, permeability and earthquake may affect general stability of underground caverns in operation period. Thus, using elasto-plastic finite difference method, three dimensional numerical simulation models of underground caverns and slope of abutment of arch dam is establised and proposed key issues are systemly studied. The calculation results show that, under reservoir storage and dam vibration subject to earthquke, abutment load has small effect on plastic zone, displacement and stress around opennings and the caverns would be stable in operation period.

Did the reservoir impoundment trigger the Wenchuan earthquake?

January 16, 2009 issue of Science magazine published, in its “ News of the Week” section, an article entitled “A Human Trigger for the Great Quake of Sichuan?”. The article boldly proposed, “Zipingpu reservoir may have triggered the Wenchuan earthquake”. Incidentally, similar reports had appeared in the media such as Telegraph website in UK and New York Times, six months after the Wenchuan earthquake. About 6 km upstream of Dujiangyan and 60 km away from Chengdu, the Zipingpu reservoir is a large-scale water control project situated on the Minjiang River in Sichuan Province. The dam was constructed in March of 2001, the water impoundment started in September of 2005, and the project was completed in 2006. As one of the few high dams in China, the rock-fill dam with reinforced-concrete face has a maximum height of 156 meters and a storage capacity of 1.112 billion cubic meters. With just dozen kilometers away from the epicenter of the M8 Wenchuan earthquake on May 12, 2008, could Zipingpu reservoir have triggered the great quake? A reservoir-triggered earthquake, or reservoir earthquake, refers to substantially enhanced seismicity (frequency and magnitude of earthquakes) near the reservoir after impoundment. The first reported earthquake triggered by reservoir occurred in 1931 near the Marathon reservoir in Greece. Since then, it has been realized that construction activities such as water impoundment or dam construction could trigger earthquakes. However, most reservoir earthquakes are moderate or weak events, presenting no great damage to the dams. Only 18 reservoirs suffered damages from reservoir-triggered earthquakes, the strongest of which registered a magnitude of M6.4. Statistics on more than one hundred cases of reservoir-triggered earthquakes show that these events share the following characteristics: (1) Epicenters of reservoir earthquake are close to the reservoir, mostly within 5 km. Their focal depths are mostly shallower than 5 km and very few deeper than 10 km. In contrast, the distance between the reservoir and the hypocenter (where the rupture starts) of Wenchuan earthquake or ruptured faults is much greater than 5 km. Zipingpu reservoir is located in a seismically active region, and at least five moderate and strong earthquakes in history had occurred nearby: the M61⁄2 Wenchuan earthquake in 1657 was within 30 km from the reservoir; the M51⁄2 Wenchuan event in 1748 was also within 30 km; the M43⁄4 Guanxian event in December of 1787 was within 5 km; the M6.2 Dayi event in February of 1970 was within 55 km; and the Lushan M4.7 event in March of 1970 was within 51 km. A digital seismic network was installed to monitor seismicity during construction of the reservoir, and seismic observation started on August 16, 2004, prior to water impoundment. The network passed evaluation and was permitted for full-scale operation started on June 27, 2005. Based on statistics of earthquake catalogs provided by the Reservoir Earthquake Institute of Sichuan Earthquake Administration, frequency and magnitude of earthquakes near Zipingpu reservoir did not change substantially since impoundment, though water levels changed. Therefore, with comparison of seismic records before and after the impoundment (i.e., October 1, 2005―April 2008, a period of two years and seven months), we think that seismicity

Stress-field constraints from recent intraplate seismicity in southeastern Australia

Well-constrained fault-plane solutions are determined for five recent moderate-magnitude intraplate earthquakes recorded in southeastern Australia: Thomson Reservoir, Tatong, Corryong and Boolarra South in Victoria, and Appin in eastern New South Wales. The solutions, determined from analysis of vertical-component first-motions, provide an indication of the maximum horizontal stress influencing contemporary regional deformation. The fault-plane solution for the 1996 M L 5.0 Thomson Reservoir earthquake indicates reverse faulting with northwest – southeast-trending horizontal compression. The Yallourn Fault is the most likely source for this event given the orientation of the fault-plane solution and the hypocentral location of the earthquake. The 1997 M L 4.2 Tatong earthquake also indicates reverse faulting with approximate north – south compression. The 1998 M L 4.7 Corryong event indicated a strike-slip mechanism with a compressional axis trending northwest – southeast. Despite local complexities identified within the stress field of the Sydney Basin, the fault-plane solution determined for the 1999 M L 4.6 Appin earthquake indicated strike-slip faulting and is consistent with the proposed weak northeast – southwest compressional regime in the region. The 2000 M L 4.7 Boolarra South earthquake indicates a mechanism consistent with reverse faulting with horizontal compression oriented northwest – southeast. Further analysis of horizontal-component seismograms indicated that the earthquake was possibly a result of movement on the Yarragon Fault. A composite focal mechanism was constructed comprising data from the four Victorian earthquakes (which lie in a similar stress province) used in this study. The solution indicated horizontal compression, consistent with reverse faulting, with an overall maximum horizontal stress trending at approximately 325°.

Application of stress-pore pressure coupling theory for porous media to the Xinfengjiang reservoir earthquakes

Theory of the coupling of stress-pore pressure in the saturated, elastic porous media is used in the study of the formation mechanism of the Xinfengjiang reservoir-induced earthquakes. Based on the results, it is believed that compared with the mechanism of additional stress in the vicinity of the reservoir, the mechanism of the coupling of additional stress and pore pressure may be more well-founded for the occurrence of reservoir-induced earthquakes.

Research on the diffusion of pore fluid andin-situ hydraulic diffusivity in the epicentral region of Xinfengjiang reservoir earthquakes

According to the fact that the Xinfengjiang reservoir earthquakes are caused mainly by water seepage, this paper using the data ofMs⩾2. 0 earthquakes, studies the hydraulic diffusivity of the mainshock zone by the expansion of the distribution area of epicenters. It is indicated thatin-situ hydraulic diffusivity during the preshock activity of the Xinfengjiang reservoir region was about 6. 2 m2/s. However, after the main shock, thein-situ hydraulic diffusivity in the main shock region increased by fifty percent, that is to say, to 9. 7 m2/s. During the long period after main shock occurrence thein-situ hydraulic diffusivity was affected by significant anisotropy of the medium and fluctuation of water level. No regularity can be found. In addition, we compare the diffusivity found by experiment with rock samples collected with thein-situ hydraulic diffusivity estimated. It is shown that the diffusivity of rock samples with fractures is about the same as the diffusivity estimatedin-situ. However, the diffusivity of whole rock samples is 3 orders of magnitudes smaller than that estimatedin-situ. Finally, we discuss the limits on the method by the expansion of distribution area of epicenters in the study of reservoir induced seismicity.

The Srinakarin Reservoir earthquake, Thailand

The Srinakarin Reservoir is situated in the west of Thailand, about 190 km northwest of Bangkok. It was completed in 1981. On 22 April 1983, an earthquake of M b 5.8 occurred at the border of the end of the a reservoir (approximately 50 km away from the dam). From comparisons of the typical characteristics of reservoir earthquakes and values of probabilistic prediction, two-step comprehensive fuzzy evaluation and estimation of maximum magnitude, we infer that this earthquake of April 1983 has been reservoir-induced. If this is true then this earthquake represents one of the most important reservoir earthquakes in the world in the 1980s.

Surface-wave studies of some South Carolina earthquakes

AbstractLong-period surface waves generated by three South Carolina earthquakes are used to infer focal mechanisms and seismic moments of the events. The 3 February 1972 Bowman, South Carolina, earthquake is found to be shallow and to require an almost strike-slip focal mechanism with pressure axes trending northeast-southwest. The 22 November 1974 Charleston, South Carolina, earthquake was smaller and was recorded by only three long-period WWSSN stations. For this earthquake, only an estimate of the seismic moment and focal depth were possible. The focal mechanism of the 2 August 1974 Clarkhill reservoir earthquake indicated motion on a northwest striking almost vertical dip-slip fault. In order to specify preferred motions on the nodal planes, full waveform modeling of the long-period traces at ATL was necessary. The results are not without ambiguity, but represent the best estimates of source parameters for these earthquakes.

RELATIONSHIP BETWEEN EARTHQUAKE MAGNITUDE AND EPICENTRAL INTENSITY IN CHINA AND ITS APPLICATIONS

This paper gives revised formulas for Chinese earthquakes, describing the relationship between earthquake magnitude, epicentral intensity and hypocentral depth, and these formulas have been derived from calculations of the data of M, I_0 and h of 57 main shocks. Data have been analyzed of foreshocks and aftershocks of several major earthquakes in North China, from which the relationships between magnitude and epicentral intensity for foreshocks and aftershocks are derived. These relationships are also calculated for earthquakes of the Xinfengjiang reservoir. A comparison between these relations indicates that each of the foreshocks, aftershocks and reservoir earthquakes possesses a specific relationship between magnitude and epicentral intensity of itself, which is systematically different from that of the mainshocks.

Reservoir conditions related to induced seismicity at the Geysers steam reservoir, northern California

abstractSeismicity at The Geysers appears to be induced by steam production, in which water boils to steam within a pervasively fractured reservoir subject to high levels of tectonic shear stresses and strains.The steam reservoir is composed of fractured Franciscan graywacke with a very heterogeneous, multiple permeability and porosity distribution. Permeability is controlled by the larger fracture systems of the reservoir, which act as a very permeable conduit to less permeable rock containing liquid water. The reservoir fluid remains close to the liquidus conditions during production, implying both a temperature and pressure decline in the rock matrix bounding the fracture systems as the reservoir is depleted.Reservoir earthquake focal mechanisms are nearly aligned with the regional tectonic strain field, and reservoir earthquakes are indistinguishable from tectonic earthquakes elsewhere in the region. Within the reservoir, the volume defined by the earthquakes has not changed within the resolution of the seismic network from 1975 to 1979. The log moment per earthquake also has not changed, suggesting a steady-state process of stress buildup and release. Added to the zero correlation of the fluid injection history with the earthquake activity, the above observations suggest that elevated pore pressures and fluid injection are not likely causes for The Geysers induced seismicity.Instead, all available evidence points to the association of induced seismicity with pore pressure and temperature declines. The two most likely mechanisms are either an increase in local shear stress levels with fissure deflation, or a transition from stable to unstable sliding (“stick-slip”). No other documented mechanism for induced seismicity are consistent with in situ reservoir conditions at The Geysers.

Modeling focal parameters for the magnitude 5.3 earthquake of the Xinfengjiang Reservoir area, People's Republic of China

abstractIn this paper, the “random test-motion adjustment” method was used for the adjustment of the triangulation net of the Xinfengjiang Reservoir earthquake area, China, and for the inversion of the focal parameters of the earthquake of magnitude 5.3. Retriangulation and leveling data of the earthquake area were thus processed. The estimated focal parameters of the earthquake are: strike, NE 62°; dip, SE at 59°; length of the fault, 4.7 km; depth of the upper boundary, 0.45 km; depth of the lower boundary, 4.5 km; dip-slip dislocation, 73.4 mm; strike-slip dislocation, 25.5 mm; seismic moment, Mo, 2.2 × 1024 dyne-cm; stress drop (Δσ), 12 bars; and the lower limit of the strain energy released (E) 1.2 × 1019 ergs. It was predominantly a normal fault. This paper concludes that the regional stress field provided the main force of the shock, whereas the stress field due to hydraulic pressure contributed the inducing force.

The 1966 Kremasta reservoir earthquake sequence

The ten-month (February-November, 1966) earthquake sequence thought to be associated with the filling of the Kremasta reservoir in northern Greece can be divided into two distinct segments. The first, consisting of the main shock ( m b =5.6, M ,=5.8) and its aftershocks in the following nine months, indicate normal faulting primarily on a northwest-striking, southwest-dipping, fault plane to a depth of 35–45 km. The second, which began in late October with another large ( m b = 5.8, M s =5.3) event, consists of thrust faulting not on the previous fault plane. The Kremasta sequence occurs at the transition between extensional and compressive faulting in a distributed plate boundary region. The main shock occurred near the top of an aftershock zone much larger than the expected fault area, in accord with a model in which the main shock and many of its aftershocks were induced by pore water diffusion along a preexisting feature. Alternatively, the main shock may be background seismicity and the aftershocks are located near the lake due to pore pressure effects. The later thrust aftershocks are less likely to be directly reservoir related.

Reservoir Loading and Earthquakes

Reservoir Loading and Earthquakes