GB 21075-2007Reservoir-induced earthquake hazard assessment (English PDF)

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents".

Drafting.

This document replaces GB/T 21075-2007 "Evaluation of Seismic Hazard Induced by Reservoirs". Compared with GB/T 21075-2007, except for the structure...

Aside from adjustments and editorial changes, the main technical changes are as follows.

a) The definition of the reservoir-induced earthquake influence zone has been changed (see 3.4, 2007 version 3.4);

b) The definition of seismic induction factors has been added (see 3.5);

c) The scope and scope of application for reservoir-induced earthquake hazard assessment have been changed (see Chapter 4, Chapter 4 of the 2007 edition);

d) The regulations for map scales have been changed (see 4.3, 5.2 and 6.1 in the 2007 edition);

e) The regulations regarding the labeling content of reservoir-induced earthquake hazard assessment maps have been revised (see 4.3, 5.1 of the 2007 edition);

f) The requirements for collecting and organizing background data on seismic activity have been revised (see 6.1, 6.3, and 7.2 in the 2007 edition);

g) The requirements for library segmentation have been changed (see 7.1, 8.1 in the 2007 version);

h) The rules for collecting probability assessment data have been changed (see 8.1, 9.1 in the 2007 version);

i) The representation of induced seismic hazard in the comprehensive assessment has been changed (see 9.3, 10.2 in the 2007 edition);

j) Table A.1 regarding the geostress environment has been added to Appendix A (see Appendix A);

k) The indices for the state of induced earthquake factors in reservoir-induced earthquakes have been modified (see Appendix C, Appendix C of the 2007 edition);

l) The attenuation relationship has been modified (see Appendix D, Appendix D of the 2007 edition).

Please note that some content in this document may involve patents. The issuing organization of this document assumes no responsibility for identifying patents.

This document was proposed by the China Earthquake Administration.

This document is under the jurisdiction of the National Earthquake Standardization Technical Committee (SAC/TC225).

Introduction

There are differing opinions in the academic community regarding the formation mechanism of reservoir-induced earthquakes, but this document does not address the controversy surrounding the causes; it only regulates the assessment of hazard.

Evaluation methods. Reservoir-induced seismic hazard assessment is an important part of the safety assessment of water conservancy and hydropower projects.

The price needs to be determined before construction based on seismic geological conditions, predicting the likelihood of earthquakes, potential reservoir sections, and maximum magnitude. It is worth noting that GB 17741 does not...

While it covers all aspects of the project, its technical specifications are insufficient to comprehensively guide this type of evaluation.

my country is one of the countries with a high incidence of reservoir-induced earthquakes, with over 60 known examples originating from reservoirs. The 1962 Xinfengjiang Reservoir earthquake was a magnitude 6.1 event.

Earthquakes cause severe disasters, which prompts related departments such as earthquake, water conservancy, and power to carry out systematic research, resulting in a series of important achievements.

Since its implementation, GB/T 21075-2007 has provided corresponding technical support for the safety of national energy strategic projects and disaster prevention and control. However, with...

With the intensive construction of high arch dam projects in the western earthquake-prone areas, the increasing spatial overlap between reservoir areas and densely populated areas, coupled with the expansion of the case database and the deepening of disciplinary understanding, the existing standards in GB/T 21075-2007 are no longer sufficient to address the risks of new engineering disasters and the sensitivity to social disasters in terms of seismic induced models and evaluation methods.

The challenges of upgrading.

This revision of GB/T 21075-2007 focuses on redefining the scope of the reservoir-induced earthquake influence zone and its application in the assessment process.

The applicable conditions in the work, the new requirements for special evaluation of expansion projects, the optimization of the state classification index of seismic induction factors, the improvement of map compilation requirements and adjustments the revised document includes the structure of risk assessment indicators, etc. It will help standardize reservoir-induced earthquake risk assessment work and enhance water conservancy...

Strengthening safety management awareness in hydropower projects will promote the healthy development of reservoir-induced earthquake hazard assessment.

Reservoir-induced earthquake hazard assessment

1 Scope

This document specifies the general requirements for reservoir-induced earthquake hazard assessment, including geological surveys of reservoir areas and seismic activity assessments in reservoir-induced earthquake-affected areas.

Technical requirements for dynamic background and geostress field investigation, as well as deterministic evaluation, probabilistic evaluation and comprehensive evaluation of seismic hazard.

This document applies to the assessment of reservoir-induced seismic hazard for newly built, renovated, and expanded reservoirs with a capacity of 1×108 m³ or more.

This method is applicable to the assessment of reservoir-induced seismic hazard in existing reservoirs or newly built, renovated, and expanded reservoirs with a capacity of less than 1×108 m³.

4 General Requirements

5 Geological survey of the reservoir area

5.1 The location, attitude, and dynamic characteristics of the main faults in the reservoir area should be verified, and relevant active fault data should be collected; and in this process...

Based on this, the fault activity was identified in accordance with the provisions of GB/T 36072.

5.2 The occurrence, density, and properties of joints should be investigated and measured, and stereographic projections or rose diagrams of the joint measurements should be drawn.

5.3 The water content, permeability, and sealing conditions of various discontinuous surfaces should be collected and analyzed.

5.4 The lithology, occurrence, assemblage relationship and hydrogeological characteristics of the reservoir area should be reviewed.

5.5 The distribution of soluble rocks in the reservoir area, as well as the degree of karst development, scale, and connectivity with the reservoir water, should be investigated.

5.6 Data on large unstable geological bodies in the reservoir area should be collected and investigated.

5.7 Information on the location, flow rate, water temperature (hot springs), and other information of springs in the reservoir area, as well as their causes, should be collected and verified.

6.Investigation of seismic activity background and geostress field in the reservoir-induced earthquake-affected area

6.1 It is necessary to investigate and collect data on earthquakes with strong or greater impact in the reservoir area and their causes, and to compile isoseismal lines and instruments for earthquakes with a magnitude greater than or equal to M4.7.

The peak ground acceleration of recorded earthquakes with strong perceptible force.

6.2 Seismic data for reservoir-induced earthquake-affected areas should be collected in accordance with the relevant provisions of GB 17741 regarding regional seismic activity assessment.

Compile an earthquake catalog. When the collected earthquake data is insufficient, locally constructed and operated seismic networks or engineering-dedicated seismic monitoring networks can be utilized.

Seismic data is used as a supplement.

6.3 The location of the epicenter of historical earthquakes in the reservoir-induced earthquake-affected area should be reviewed.

6.4 When a regional or local seismic network cannot control a reservoir-induced earthquake of magnitude 1.0 or greater within the affected area, procedures should be followed before impoundment.

GB/T 31077 stipulates the construction of a reservoir seismic monitoring network to monitor the background seismic activity in the reservoir-induced earthquake-affected area. (Reservoir earthquakes) the monitoring network should ideally be completed and operational one year before water storage.

6.5 The following requirements shall be met when conducting a geostress field survey in the reservoir-induced earthquake-affected area.

a) Obtain historical earthquake focal mechanism solutions for the reservoir-induced earthquake-affected area and adjacent areas, including comprehensive fault plane solutions for small earthquakes;

b) Obtain in-situ stress information in the reservoir-induced earthquake-affected area and adjacent areas, and conduct field surveys and supplementary investigations when necessary;

c) When the historical earthquake focal mechanism solutions and in-situ stress information of the reservoir-induced earthquake-affected area and adjacent areas can determine the in-situ stress of the reservoir area...

When in a stress environment, it should be adopted.

6.6 When it is difficult to determine the geostress environment in the reservoir area and data is insufficient, deep borehole in-situ stress measurement shall be carried out in accordance with the provisions of DB/T 14.

7 Deterministic Evaluation

8 Probability Evaluation

8.1 Data on reservoir-induced earthquakes from both domestic and international sources should be collected, and a certain number of large-scale engineering projects where reservoir-induced earthquakes have not occurred should be randomly selected.

For example, they together form the sample set. The proportion of reservoir-induced earthquake cases in the sample set to the total number of samples should not be less than 12%. The total number of samples should not be less than [a certain percentage].

There are 500.

8.2 Seismic induction factors should be selected from Appendix C to form a set of seismic induction factors. Among these, the basic seismic induction factors include reservoir capacity, reservoir depth, and lithological combination.

Or rock mass structure type, tectonic stress environment or geostress state, fault activity. The set of seismic induction factors should contain at least 5 basic seismic inductions.

factor.

8.3 Induced seismic factors are represented by their "states." Each induced seismic factor can be divided into several states, but should be divided into at least two states. Induced seismic factors the state division should comply with the provisions of Appendix C.

8.4 The predicted maximum magnitude of reservoir-induced earthquakes should be categorized (divided into several intervals), with at least two categorizations. Magnitude categorization it is advisable to take into account both the magnitude interval and the number of samples within the grade interval.

8.5 The induced earthquake factors and their states for different magnitude ranges of the sample should be statistically analyzed. The different states of each induced earthquake factor should be grouped together.

The combination of inducing factors that constitute this magnitude earthquake is determined, and their probability of occurrence is statistically analyzed.

8.6 The induced earthquake factors and their states for each section of the reservoir being assessed should be analyzed. Each induced earthquake factor should be analyzed in detail.

The state constitutes the combination of seismic induction factors for this reservoir section.

8.7 The probability of earthquake occurrence for different magnitudes in each reservoir section should be calculated according to formula (1).

9 Overall Evaluation

9.1 A comprehensive evaluation of the maximum magnitude of induced earthquakes in each section of the reservoir should be conducted. When the results of deterministic and probabilistic evaluations are inconsistent, the deterministic evaluation should prevail.

The conclusions are primarily based on deterministic evaluations.

9.2 The maximum magnitude of the reservoir-induced earthquakes in each reservoir section should be comprehensively evaluated to assess the overall risk of reservoir-induced earthquakes.

9.3 The peak ground acceleration (PGA) of reservoir-induced earthquakes should be given. The relationship between PGA and magnitude should be determined according to Appendix D.