GB/T 39419-2020.Grades of tsunami.
1 Scope
GB/T 39419 specifies the determination and classification methods of tsunami intensity grades and earthquake tsunami energy levels.
GB/T 39419 is applicable to the monitoring and assessment of tsunami disasters, scientific research and news reporting.
2 Terms and definitions
The following terms and definitions apply to this document.
2.1
Tsunami
Long-period, small-amplitude gravity waves aroused by underwater earthquakes, volcanic eruptions or underwater collapses and landslides, which reach the shore at a speed of hundreds of kilometers per hour, forming huge waves with great ferocity and damage.
Note: Rewrite GB/T 15920-2010, definition 2.5.60.
2.2
Tsunami amplitude tsunami amplitude
The absolute value of the difference between the tsunami peak (trough) and the undisturbed sea level at that time.
2.3
Tsunami intensity tsunami intensity
The degree of impact of a tsunami process on a coastal area.
Note: Generally, it can be divided based on the tsunami amplitude observed by the coastal tide station.
2.4
Tsunami energy level tsunami magnitude
The measure of natural energy released during the tsunami generation process.
3 Tsunami level types
3.1 Tsunami intensity level
Tsunami intensity levels are divided according to the degree of impact of tsunami on a coastal area.
3.2 Tsunami Energy Level
Tsunami energy levels are divided according to the energy released by earthquake tsunamis.
6 Level Selection Method
When determining the tsunami level, you can choose from the tsunami intensity level or earthquake tsunami energy level according to different needs. The selection method is as follows:
a) When it is necessary to obtain the intensity of the tsunami disaster affected by a certain coastal area, the method of calculating the average tsunami amplitude Hav in the area in 4.1 is used to determine the tsunami intensity; combined with the post-disaster on-site investigation of the affected area, the possible impact of the tsunami intensity level in Table 1 in 4.2 can be referred to for the description of the possible impact of the tsunami intensity level to evaluate the disaster-causing impact of the tsunami event;
b) When it is necessary to measure the overall size of an earthquake tsunami event, the tsunami energy level method in Chapter 5 is used to calculate the tsunami level; each earthquake tsunami event has a unique energy level scale.
This standard specifies the determination and classification methods of tsunami intensity levels and earthquake tsunami energy levels. This standard applies to monitoring and assessment, scientific research and news reporting of tsunami disasters.

ICS07.060
National Standard of the People's Republic of China
GB/T39419—2020
Tsunami Grades
Grades of tsunami
Issued on 2020-11-19
State Administration for Market Regulation
National Standardization Administration
Implementation on 2021-06-01
This standard was drafted in accordance with the rules given in GB/T1.1-2009. This standard was proposed by the Ministry of Natural Resources of the People's Republic of China. This standard is under the jurisdiction of the National Technical Committee for Marine Standardization (SAC/TC283). The drafting unit of this standard is the National Marine Environmental Forecast Center. The main drafters of this standard are Fan Tingting, Yuan Ye, Zhao Lianda, Gan Peitao, Gan Juncheng, and Hou Jingming. GB/T39419—2020
1 Scope
Tsunami Level
This standard specifies the determination and classification methods of tsunami intensity levels and earthquake tsunami energy levels. This standard is applicable to the monitoring and assessment of dry sea disasters, scientific research and news reporting. Terms and Definitions
The following terms and definitions apply to this document. 2.1
tsunami
GB/T39419—2020
Long-period, small-amplitude gravity waves aroused by underwater earthquakes, volcanic eruptions, or water subsidence and landslides reach the shore at a speed of hundreds of kilometers per hour, forming huge waves with great harm. Note: Rewrite GB/T15920-2010 definition 2.5.60. 2.2
tsunamiamplitude
Tsunami amplitude
The absolute value of the difference between the tsunami wave crest (trough) and the undisturbed sea level at that time. 2.3
Tsunami intensity
tsunami intensity
·The degree of impact of a tsunami process on a certain coastal area. Note: Generally, it can be divided based on the tsunami amplitude observed by the coastal tide station. 2.4
tsunamimagnitude
Tsunami energy level
The measure of natural energy released during the tsunami generation process. Tsunami level type
Tsunami intensity level
It is divided according to the degree of impact of the tsunami on a certain coastal area. 3.2
Tsunami energy level
Tsunami intensity is divided according to the tsunami energy level based on the energy released by the earthquake tsunami
Average amplitude calculation
Calculated based on the average value of the maximum tsunami amplitude observed by the tide station on a certain coast section. The calculation method is shown in formula (1): Hav
（1）
GB/T39419—2020
Where:
The average value of the maximum tsunami amplitude observed by each tide station on the coast section, in meters (m); H, - the maximum tsunami amplitude observed by the ith tide station on the coast section, in meters (m). 4.2
Tsunami intensity level classification
Based on the average size H of the maximum tsunami amplitude in a certain coastal area and the macroscopic impact that the tsunami may cause, the tsunami intensity is divided into 6 levels, corresponding to levels I, II, III, IV, V and V, respectively, as shown in Table 1. Table 1
Tsunami intensity level
Tsunami intensity level
Average tsunami amplitude (H.)
10~≤20
Degree of impact
Major disaster
Very strong
Very slight
Description of possible impact
Casualties occurred along the coast, all ships were severely damaged, and all coastal structures were severely damaged. Fires, leakage of hazardous chemicals and other secondary disasters were serious, and coastal shelterbelts were ineffective
Casualties occurred along the coast, most ships were damaged, and most coastal structures were severely damaged. Farmland was destroyed, coastal shelterbelts were partially destroyed, a large number of marine aquaculture facilities were washed out to sea, and port projects were severely damaged
Casualties occurred along the coast, most ships were damaged, some ships collided with each other, and some shore structures were damaged. The coastal protection forest is slightly damaged, and a large number of marine aquaculture facilities are affected
Everyone along the coast can feel it, some ships rush to the coast, collide with each other or capsize, and the shore structures and protective facilities are slightly damaged
Some people on the shore and on the boats can feel it, and a few ships are affected by the coastal waves and currents, and the coastal structures are not damaged
No one along the coast or people on very few ships can feel it, no need to evacuate, and there is no impact on the sea and coastal objects
Note; "very few" means less than 10%, "few" means 10% to 40%; "some" means 40% to 70%; "most" means 70% to 90%; "most" means more than 90%.
5 Tsunami Energy Level
The tsunami energy level is calculated based on the amount of natural energy released during the tsunami generation process. Calculated by formula (2): M,=0.41log1o(E,×107)-0.38
Where:
Tsunami energy level;
Total tsunami potential energy, in joule (J). The tsunami energy level is retained to one decimal place. For the determination of the tsunami energy level formula and its constants, see Appendix A. Where E, the calculation of the total tsunami potential energy, see formula (3): E
Where:
Number of unit sources in the finite fault solution; bzxZ.net
(2)
·(3)
E, the tsunami potential energy of a single unit source, in joule (J). E: Calculated by formula (4):
E,=1/2pgh?△S
Wherein:
——the density of seawater is 1.03×10\, in kilograms per cubic meter (kg/m\); the acceleration of gravity is 9.8, in meters per second squared (m/s2); h: the vertical dislocation height of a single unit source fault, in meters (m); △S: the area of ​​a single unit source rupture surface, in square meters (m\). GB/T39419—2020
. (4)
Based on the finite fault solution of earthquake tsunami events, h: is calculated based on the elastic dislocation theory fault model, and the fault is divided into n rectangular unit sources with a certain length and width. The area of ​​a single unit source is △S, which is expressed by formula (5): AS=aXb
Where:
a—-single unit source length, in meters (m); single unit source width, in meters (m). 6
Level selection method
......5)
When determining the tsunami level, according to different needs, you can choose from the tsunami intensity level or the earthquake tsunami energy level. The selection method is as follows:
When it is necessary to obtain the intensity of the tsunami disaster in a coastal area, the method of calculating the average tsunami amplitude H. in the area in 4.1 is used to determine the tsunami intensity; combined with the post-disaster on-site investigation of the affected area, the possible impact of the tsunami intensity level in Table 1 in 4.2 can be used to evaluate the disaster-causing impact of the tsunami event; when it is necessary to measure the overall size of an earthquake tsunami event, the tsunami energy level method in Chapter 5 is used to calculate the tsunami level; each earthquake tsunami event has a unique energy level scale. 3
GB/T39419—2020
Appendix A
(Informative Appendix)
Basis of the tsunami energy level formula
In the calculation of tsunami energy level, based on the finite fault solution of earthquake sea events in the Finite-Source Rupture Model Database (URL: http://equake-rc.info/), all earthquake tsunami events with moment magnitude greater than 6.5 (inclusive) from 1960 to 2017 (39 in total) were screened, and each event was divided into rectangular unit sources with a certain length and width. Taking the magnitude 9.0 earthquake tsunami event in eastern Japan on March 11, 2011 as an example, Yue and Lay[4I divided the earthquake fault into 112 unit sources, each with a length and width of 30 km (see Figure A.1). Using the tsunami potential energy formula (3), the total potential energy E of this earthquake tsunami event is calculated.
Japan Tohoku Earthquake M.9.0
Latitude/longitude/depth: 38.11°, 142.92°, 20.0km70
X: East-West direction [km]
Y: North-South direction [km]
Figure A.1 Finite fault division structure diagram of the M9.0 earthquake in eastern Japan300
Based on the theoretical basis of Murty and Loomis[s], the linear logarithmic relationship between the earthquake moment magnitude M and the tsunami potential energy E, is obtained by calculating the tsunami potential energy of 39 earthquake tsunami events using the finite fault solution (see Figure A.2). Figure A.2The red dot in 2 represents an earthquake tsunami event, from which the earthquake tsunami energy level relationship is obtained, see formula (A.1): M, = alogio (E, × 10') + b
, where a is 0.41, b is -0.38, and the linear correlation coefficient of the relationship is 0.9464. 4
......( A.1 )
logio（E,×107)
Linear logarithmic relationship between earthquake moment magnitude and tsunami potential energy Figure 23
GB/T39419—2020
GB/T39419—2020
References
GB/T15920-2010 Oceanographic terminology Physical oceanography GB17740—2017 Provisions for earthquake magnitude
GB/T17742—2008 China Earthquake Intensity Scale[4]
Yue, H. and T. Lay. 2013. Source Rupture Models for the Mw 9.0 2011 Tohoku Earthquake from Joint Inversions of High-Rate Geodetic and Seismic Data, Bull. Seism. Soc. Am.,103, 1242-1255.[5]Murty,TS,Loomis,HG1980.A new objective tsunami magnitude scale.Mar.Geod.,4(3),267-282.
Nosov,MA,Bolshakova,AV,&Kolesov,SV,2o14.Displaced water volume, potential energy of initial elevation, and tsunami intensity: Analysis of recent tsunami events, Pure andAppliedGeophysics, 171(12), 3515-3525.6
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