A Reservoir Seismic Impact Analysis Method Based on Historical Data

Abstract

This invention discloses a method for analyzing the impact of reservoir earthquakes based on historical data. It comprises the following steps: Step 1, determining the range of reservoir earthquake occurrence; Step 2, obtaining historical data on reservoir earthquakes within the region; Step 3, determining the impact basis using the historical data; Step 4, determining the impact of reservoir earthquake focal depth within the region; Step 5, calculating the impact of reservoir earthquakes. This invention, by analyzing historical data, can more accurately predict the impact of reservoir earthquakes, providing a scientific basis for the safe management of reservoirs.

Description

Technical Field

[0001] This invention relates to the field of reservoir earthquake impact analysis technology, and specifically to a method for reservoir earthquake impact analysis based on historical data. Background Technology

[0002] After a reservoir is built, the surrounding geological environment undergoes significant changes, leading to erosion and damage under the periodic influence of reservoir water levels. Simultaneously, fluctuations in reservoir water levels alter groundwater pressure along the reservoir banks, resulting in various geological damage phenomena such as bank erosion, collapse, landslides, and abrasion. In some areas, reservoir-induced earthquakes may even occur frequently. Reservoir-induced earthquakes differ from natural earthquakes. They are mostly caused by changes in water levels following the impoundment of artificial reservoirs or dams, altering the original geological conditions of the reservoir and its surrounding areas. They are a type of geological hazard closely related to human activities, especially reservoir engineering. Historically, some high-magnitude and impactful reservoir-induced earthquakes include the 1962 Xinfengjiang (Ms. 6.1) reservoir earthquake in Guangdong; the 1963 Kariba (Ms. 6.1) reservoir earthquake in Zambia; and the 1966 Krymasta (Ms. 6.3) reservoir earthquake in Greece. In the 1990s, to accelerate economic development and meet the demand for electricity, my country entered a peak period of hydropower station construction. After most hydropower stations impounded water, the frequency of reservoir-related earthquakes increased significantly. Furthermore, due to the shallow focal depth of reservoir-related earthquakes, their impact and damage to ground structures were far greater than those of natural earthquakes of the same magnitude. Currently, the analysis of reservoir-related earthquakes still relies on relatively traditional methods for analyzing natural earthquakes. While this method can comprehensively analyze traditional natural earthquakes, the analysis process is complex, computationally time-consuming, and generally only applicable to single, large-magnitude earthquakes, making it unsuitable for smaller, more frequent reservoir-related earthquakes. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a method for analyzing the impact of reservoir earthquakes based on historical data, so as to solve the problems mentioned in the background art.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for analyzing the seismic impact of reservoirs based on historical data, which includes the following steps:

[0005] Step 1: Determine the area where the reservoir earthquake will occur;

[0006] Step 2: Obtain historical earthquake data for reservoirs in the region;

[0007] Step 3: Determine the underlying factors by using historical earthquake data related to the reservoir;

[0008] Step 4: Determine the impact of reservoir-induced earthquake focal depth in the region;

[0009] Step 5: Calculate the impact of reservoir earthquakes.

[0010] Further, step 1 specifically includes: taking the distance R from the farthest reservoir earthquake that may have a significant impact on the region as the generation radius of the reservoir earthquake, and using the region as the center and R as the radius to delineate the generation range of the reservoir earthquake; if the impact distance R of the reservoir earthquake in the region is less than 40km, 40km can be taken as the radius to delineate the generation range of the reservoir earthquake.

[0011] Furthermore, step 2 specifically includes:

[0012] Raw data on reservoir earthquakes since their occurrence were obtained from local stations. The data were divided into different periods based on the premise that the geological conditions in the region had not changed significantly, and a reservoir earthquake catalog was compiled.

[0013] Furthermore, step 3 specifically includes: based on reservoir earthquake databases from different periods, selecting the reservoir earthquake S that had the most severe impact during that period. i , where i is a positive integer representing different periods;

[0014] Let the seismic wave energy during a reservoir earthquake be E. S Using the empirical formula for energy and magnitude, we have:

[0015] lgE S =1.5M s +4.4 (1)

[0016] In the formula, M s The magnitude is M (surface wave magnitude). s The observable focal depth is relatively shallow (h≤60km), making it suitable for determining the magnitude of shallow-focus earthquakes;

[0017] Calculate E for each period Si Set the impact base to E Sa Then we have:

[0018]

[0019] Among them, the impact on basic E Sa Δ is the average value for each period. i This is the epicentral distance.

[0020] Furthermore, step 4 specifically includes: Since reservoir earthquakes mostly have a focal depth of less than 15 km, they are shallow-focus earthquakes, and the impact of changes in focal depth is relatively small. Therefore:

[0021]

[0022] In the formula h i For event S iThe focal depth, h is the focal depth of a certain reservoir earthquake, and δ is the depth influence coefficient.

[0023] Furthermore, step 5 specifically includes:

[0024] Assuming that no major geological disasters occur in this region and the geological conditions remain relatively stable, the impact of reservoirs on earthquakes in this region can be analyzed as follows:

[0025]

[0026] Here, F is the influencing variable and the F value is greater than 0. The larger the F value, the more severe the impact of a reservoir earthquake.

[0027] Beneficial effects of this invention:

[0028] 1. Improve prediction accuracy: By analyzing historical data, the impact of reservoir earthquakes can be predicted more accurately, providing a scientific basis for the safe management of reservoirs.

[0029] 2. Risk reduction: By analyzing the impact of earthquakes on reservoirs, early warnings can be issued, reducing the potential risks that earthquakes may pose to reservoirs and their surrounding environment.

[0030] 3. Optimize resource allocation: Reservoir earthquake impact analysis methods based on historical data can help decision-makers allocate resources rationally and improve their ability to respond to earthquake disasters.

[0031] 4. Promote technological innovation: The research methods and results of this invention can provide reference and inspiration for technological innovation in related fields, and promote the development of reservoir earthquake impact analysis technology.

[0032] 5. Improve emergency response capabilities: By analyzing the impact of reservoir earthquakes, this invention can improve the emergency response capabilities of governments and relevant departments during earthquakes, thereby reducing earthquake disaster losses. Attached Figure Description

[0033] Figure 1 This is a flowchart of a method for analyzing the earthquake impact of a reservoir based on historical data. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0035] Example 1: This example provides a reservoir earthquake impact analysis method based on historical data, used to analyze the impact of reservoir earthquakes on ground structures around the reservoir area after the dam and reservoir impoundment. This analysis method mainly determines the impact of a reservoir earthquake on a certain region by calculating the reservoir earthquake impact variable F. The impact variable F takes a value greater than 0; the larger the F value, the more severe the impact. The impact of this reservoir earthquake on the region can be determined by the F value. Specifically, it includes the following steps:

[0036] Step 1: Determine the area where the reservoir earthquake will occur;

[0037] The distance R from the epicenter of the highest-magnitude reservoir-generated earthquake in the region is used as the generation radius of the reservoir-generated earthquake. The region is then used as the center and R as the radius to delineate the generation range of the reservoir-generated earthquake. Using a circle as the generation range of the reservoir-generated earthquake allows for a more comprehensive consideration of the impact of reservoir-generated earthquakes from different directions on the region compared to other shapes. All reservoir-generated earthquakes that affected the region during this period are added to the database, improving the reliability of the analysis results.

[0038] Reservoir-induced earthquakes occur more frequently than natural earthquakes, but they are more significantly affected by geological changes. Reservoir-induced earthquakes generally occur within a few kilometers of the reservoir or dam, with shallow focal depths; most reservoir-induced earthquakes have a focal depth of less than 10 km, and their impact area is relatively small. According to the "Technical Specification for Regional Tectonic Stability Investigation of Hydropower and Water Conservancy Projects" (DLT5335-2006), the scope considered in reservoir-induced earthquake impact analysis should be no less than 40 km. If the impact distance R of reservoir-induced earthquakes in the region is less than 40 km, a radius of 40 km can be used to define the occurrence range of reservoir-induced earthquakes.

[0039] Step 2: Obtain historical earthquake data for reservoirs in the region;

[0040] Raw data on reservoir-induced earthquakes since their occurrence were obtained from local stations. The data was divided into different periods, with the timeframe defined by the absence of significant changes in local geological conditions. If the period was long, it could also be divided into periods such as years. The collected data was standardized in format and reorganized to obtain a new reservoir-induced earthquake catalog. Compared to establishing a single reservoir-induced earthquake database, using geological conditions as the data division boundary allows for a better understanding of the main causes, patterns, and trends of local reservoir-induced earthquakes under specific geological conditions, enabling the development of corresponding disaster prevention and mitigation measures. Furthermore, analysis of historical data reveals changes in local hydrology, geology, and architecture, allowing for more accurate predictions of future reservoir-induced earthquakes and enabling the implementation of appropriate preventative measures to reduce losses to some extent.

[0041] Step 3: Determine the underlying factors by using historical earthquake data related to the reservoir;

[0042] Most reservoir-induced earthquakes exhibit a series of characteristics, including foreshocks, mainshocks, and aftershocks. Reservoir-induced earthquakes generally occur shortly after reservoir impoundment. Foreshocks are primarily small earthquakes, gradually increasing in number. The mainshock is most likely to occur within the first or second cycle of the reservoir's highest water level. Compared to foreshocks and aftershocks, using the mainshock as the basis for analysis allows for a more accurate assessment of the impact of larger reservoir-induced earthquakes on the region. The mainshocks at different times are denoted as reservoir-induced earthquake events S. i Where i is a positive integer, representing different periods, denoted by S i This serves as the basis for understanding the impact of reservoir earthquakes during period i.

[0043] Using the energy generated during a reservoir-induced earthquake as a criterion, the greater the energy generated, the more severe its impact on ground structures is considered to be. Based on this standard, the reservoir-induced earthquake database established in step 2 is used to select the reservoir-induced earthquake event S with the strongest impact on the region during different periods. i Where i is a positive integer, representing different periods, and the event S is calculated. i The energy produced.

[0044] Event S i Let the energy generated when it occurs be E. S Then we have:

[0045] lgE S =1.5M s +4.4 (1)

[0046] In the above formula, M s The magnitude is M (surface wave magnitude). s The observable focal depth is relatively shallow (h≤60km), making it suitable for determining the magnitude of shallow-focus earthquakes.

[0047] Reservoir earthquakes are strongly correlated with regional geological conditions. When geological changes are active in the region or the reservoir has been in use for a long time, multiple databases from different periods exist. Using the average value of each period as the basis for analysis can improve the accuracy of the analysis to some extent.

[0048] Calculate E for each period Si Set the impact base to E Sa Then we have:

[0049]

[0050] In the above formula, the influence of the basic E Sa Δ is the average value for each period. i This is the epicentral distance.

[0051] Step 4: Determine the impact of reservoir-induced earthquake focal depth in the region;

[0052] The impact of reservoir-induced earthquakes is related not only to the energy released during the earthquake but also to the focal depth. Focal depth refers to the vertical distance from the earthquake source to the ground. Based on focal depth, earthquakes can be classified as: shallow-focus earthquakes (0-60 km); intermediate-focus earthquakes (60-300 km); and deep-focus earthquakes (greater than 300 km).

[0053] Most reservoir earthquakes are caused by the impoundment of water in reservoirs. The stress generated by the water is much smaller than that of tectonic stress. Consequently, the focal depth of reservoir earthquakes is generally no more than 15 km, which are shallow-focus earthquakes with a relatively small range of variation. Therefore, the impact caused by changes in focal depth is relatively small compared to the impact caused by changes in other factors.

[0054] Therefore, the depth influence coefficient δ is:

[0055]

[0056] In the above formula, h i For event S i The focal depth, h is the focal depth of a certain reservoir earthquake, and δ is the depth influence coefficient.

[0057] Step 5: Calculate the impact of an earthquake on the reservoir;

[0058] Combining steps 3 and 4, assuming that no major geological disasters occur in this region and that geological conditions remain relatively stable, the impact of reservoir earthquakes on this region can be analyzed as follows:

[0059]

[0060] Here, F is the influencing variable and the F value is greater than 0. When F is greater than 0 and less than 0.5, it is a stage with a small influence. When F is greater than 0.5 and less than 1, it is a stage with a gradually increasing influence. When F is greater than 1, it is a stage with a strong influence. The larger the F value, the more severe the influence.

[0061] Example 2: A certain water conservancy project is located in the southwest region and is a large-scale water conservancy project. The total storage capacity of the reservoir is approximately 12 billion cubic meters. 3 The reservoir's normal water level is 600.00m, and it is geographically located in the transition zone between the Qinghai-Tibet Plateau, the Yunnan-Guizhou Plateau, and the Sichuan Basin. Before impoundment, the area where the reservoir is located was a high-incidence earthquake zone, with frequent earthquakes, the largest magnitude of which reached Ms5.3.

[0062] Impact Analysis

[0063] Step 1: Determine the range of reservoir-induced earthquakes. Calculate the location of the largest reservoir-induced earthquake in the region. The largest reservoir-induced earthquake in the region is Ms5.3. Using latitude and longitude calculations, the epicentral distance of this earthquake to the region is approximately 25 km. Using the same method, calculate the epicentral distances of the previous five earthquakes in the region: 25 km, 37 km, 30 km, 38 km, and 35 km, respectively. All these results are less than 40 km. Therefore, 40 km is selected as the calculation radius for reservoir-induced earthquakes in this region.

[0064] Step 2: Obtain historical reservoir earthquake data for the region. Analysis and calculation using this method require collecting information such as the occurrence time, magnitude, focal depth, and epicentral distance of reservoir earthquakes in the region. Raw data since the occurrence of reservoir earthquakes is obtained from local seismic stations, and the occurrence of reservoir earthquakes in the region over the past 10 years is collected in conjunction with seismic networks. Some data are shown in the table below:

[0065]

[0066] Step 3: Determine the influencing factors using historical earthquake data of the reservoir. Through preliminary analysis of the data established in Step 2, the obtained data can be divided into five cycles with a two-year period, as shown in the table below.

[0067]

[0068] Calculate E in each period S Value, calculate the influence of the basic E Sa :

[0069]

[0070] Step 4: Determine the impact of reservoirs on earthquake focal depth within the region. To calculate the depth impact coefficient, we can first obtain h. sa The depth influence coefficient δ can be determined through... The calculation yielded the result. Where h represents the focal depth of a specific reservoir earthquake.

[0071] Step 5: Calculate the impact of reservoir earthquakes. Taking a reservoir earthquake S as an example: Ms is 4.7, the focal depth is about 10km, the epicentral distance is about 38km. When it occurs, there is obvious tremor indoors, some items indoors shake, and unsecured objects fall to the ground.

[0072] calculate Substitute

[0073] In example S, the F value is 1.153, which belongs to the stage of strong influence.

[0074] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for analyzing the seismic impact of reservoirs based on historical data, characterized in that: It includes the following steps: Step 1: Determine the area where the reservoir earthquake will occur; Step 2: Obtain historical earthquake data for reservoirs in the region; Step 3: Determine the underlying factors by using historical earthquake data related to the reservoir; Step 4: Determine the impact of reservoir-induced earthquake focal depth in the region; Step 5: Calculate the impact of an earthquake on the reservoir; Step 3 specifically includes: based on reservoir earthquake databases from different periods, selecting the most severe reservoir earthquakes within that period. ,in A positive integer, representing different periods; Set the seismic wave energy during a reservoir earthquake as... Using the empirical formula for energy and magnitude, we have: （1）； In the formula, Surface wave magnitude, The observable focal depth is relatively shallow, i.e., the focal depth h≤60 km, which is suitable for determining the magnitude of shallow-focus earthquakes; Calculate each period Set the impact base as Then we have: （2）； Among them, the impact on the foundation This represents the average value across different periods. The epicentral distance; Step 4 specifically includes: Since most reservoir earthquakes have a focal depth of less than 15 km, they are shallow-focus earthquakes, and the impact of changes in focal depth is relatively small. Therefore: （3）； In the formula For the event focal depth, The focal depth of a certain reservoir earthquake. This represents the depth of influence coefficient. Step 5 specifically includes: Assuming that no major geological disasters occur in this region and the geological conditions remain relatively stable, the impact of reservoirs on earthquakes in this region can be analyzed as follows: （4）； in, For the influencing variables and When the value is greater than 0, The larger the value, the more severe the impact of a reservoir earthquake.

2. The method for analyzing the seismic impact of reservoirs based on historical data according to claim 1, characterized in that: Step 1 specifically includes: taking the distance R from the farthest reservoir earthquake that may have a significant impact on the region as the generation radius of the reservoir earthquake, and using the region as the center and R as the radius to delineate the generation range of the reservoir earthquake; if the impact distance R of the reservoir earthquake in the region is less than 40km, 40km can be taken as the radius to delineate the generation range of the reservoir earthquake.

3. The method for analyzing the seismic impact of reservoirs based on historical data according to claim 1, characterized in that: Step 2 specifically includes: Raw data on reservoir earthquakes since their occurrence were obtained from local stations. The data were divided into different periods based on the premise that the geological conditions in the region had not changed significantly, and a reservoir earthquake catalog was compiled.

Images