GB 17740-1999 Provisions on earthquake magnitude

This standard is the determination method and use regulations of earthquake magnitude M, which is applicable to social applications such as earthquake determination, earthquake prediction, earthquake disaster prevention and reduction, and news reporting. GB 17740-1999 Earthquake Magnitude Regulations GB17740-1999 Standard Download Decompression Password: www.bzxz.net

III. General ruler for earthquake magnitude GB17740—1999 Approved and issued by: State Administration of Quality and Technical Supervision Date of issue: April 26, 1999 Implementation date: November 1, 1999 3—1—2 3—1—3 -1—4 3—1—4 Determination method of earthquake warm magnitude M Use regulations This standard is formulated based on the principles of earthquake magnitude determination in the current China Earthquake Administration's "Specifications for Seismic Station Observation" (1990). The purpose of formulating this standard is to standardize the determination and social application of earthquake magnitude.
When formulating this standard, we drew on the methods of measuring and reporting earthquake magnitude of major international earthquake monitoring and reporting institutions and the earthquake observation specifications of the China Earthquake Administration, compared the advantages and disadvantages of different plans, and widely solicited the opinions of relevant experts. This standard follows the provisions of China's earthquake magnitude measurement to ensure that the quantitative magnitude system of my country, which has been widely used by the society, can be continued. This standard is proposed and managed by the China Earthquake Administration. The drafting units of this standard are: Institute of Geophysics, China Earthquake Administration, Institute of Crustal Stress, China Earthquake Administration.
The main drafters of this standard are: Xu Shaoxie, Lu Yuanzhong, Guo Lucan, Chen Peishan, Xu Zhonghuai, Xiao Chenglang, Feng Yijun. This standard was first issued on April 26, 1999. 3-1-3
1 Scope
This standard is the provisions for the determination method and use of earthquake magnitude, which is applicable to social applications such as earthquake measurement, earthquake prediction, disaster prevention and reduction, and news reporting.
This standard does not restrict the use of other types of magnitudes in scientific research and analysis. "Earthquake magnitude M" is the magnitude specified in this standard. Other types of magnitudes must be prefixed with restrictive words and supplementary notes. For example: body wave magnitude mb, near earthquake magnitude ML, moment magnitude Mw, etc. Earthquake magnitude M is measured by seismic surface waves. When deep earthquakes (focal depth greater than 70km) and small earthquakes cannot be measured by seismic surface waves, they can be measured by mb and ML as specified in the "Observation Specifications for Seismic Stations" (1990). 2 Definitions
This standard adopts the following definitions.
2.1 Earthquake magnitude Earthquake magnitude is a relative measure of the size of an earthquake.
2.2 Surface wave surface wave
Seismic waves propagating along the surface of the earth excited by the earth. 2.3 Particle motion
The motion of any point on the earth when an earthquake wave passes through. 2.4 Displacement of ground motion The distance of a ground particle relative to its original stationary point when it moves. 2.5 Velocity of particle motion The derivative of its ground displacement with respect to time when a particle moves. 2.6 Epicentral distance The distance from the epicenter to a specified point on the ground. 2.7 Calibration function The correction value required to measure the magnitude of a seismic event at different epicentral distances using the maximum value of the particle motion velocity is equivalent to the magnitude of the corresponding event when the particle motion velocity is 1 μm/s at this distance.
3 Method for determining the magnitude of an earthquake
The magnitude of an earthquake is determined by the maximum value of the particle motion of the ground wave (A/T)max.
Calculation formula:
M = lg (A/T)max +a (△)
Where A-the maximum ground displacement of the earthquake surface wave, take the vector sum of the ground displacements of the two horizontal directions, μm;
corresponding period, s;
-capsule distance, (\).
When measuring the two horizontal components of the maximum ground displacement, take the vibrations at the same time 3-1-4
or with a period difference within 1/8 of a week. If the periods of the two components are not consistent, take the weighted sum:
T= (TnAN+TeAE) /(An+AE)
North-South ground displacement, um;
-East-West ground displacement, um;
T-the corresponding period of A, s;
-the corresponding period of Aε, s.
Gauge function. (△) is:
g (4) =1.66lg4 +3.5
The period that differs greatly from the value given in Table 1 should not be used to determine the earthquake magnitude M.
The earthquake magnitude M should be determined based on the average value of multiple stations. Table 1
Selected earthquakewww.bzxz.net
Surface wave period (T) values ​​without considering the epicentral distance (4)
4Usage regulations
Earthquake information provision
12 ~18
12 ~20
16 ~ 22
16 ~ 22
13018~25
When the earthquake work departments or institutions at all levels provide earthquake information, the earthquake magnitude specified in this regulation should be used.
4.2Earthquake news reports
When news agencies report earthquake news in my country, the earthquake magnitude specified in this regulation should be used.
Release of earthquake forecast
Governments at all levels shall use the earthquake magnitude specified in this regulation when releasing earthquake forecasts and departments or institutions at all levels working on earthquakes formulate earthquake monitoring and forecasting plans.
4.4 Disaster prevention and reduction
Governments at all levels and departments or institutions working on earthquakes at all levels shall use the earthquake magnitude specified in this regulation when formulating earthquake prevention and disaster reduction plans and implementing earthquake prevention and disaster reduction measures.
4.5 Recognition of earthquake magnitude
For social application, the earthquake magnitude M recognized by the earthquake administrative department of the State Council shall prevail.
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