Study On The Rapid Determination Method Of Energy Magnitude And Its Application

Seismic radiated energy E_S is an important physical quantity.The measurement of seismic radiated energy is an important basic problem in the quantitative research of earthquakes and an important research topic in digital seismology.It has a non-negligible impetus to the research of earthquake quantification and engineering seismology.The energy radiated by earthquakes in the form of seismic waves is mainly concentrated near the corner frequency of the source spectrum,so the seismic radiated energy E_S is more suitable for describing the potential destructiveness of earthquakes.The energy magnitude M_e is the magnitude converted from the seismic radiated energy E_S,and there is no problem of magnitude saturation.The energy magnitude M_e is closely related to the seismic energy that caused the disaster and is more suitable for describing the potential destructiveness of the earthquake.If the seismic radiated energy E_S and energy magnitude M_e can be measured in a short time after a great earthquake,it has important reference significance for earthquake disaster assessment and earthquake emergency response.And to do that,the main work of this paper is as follows:First of all,based on the attenuation characteristics of seismic waves,a program is designed to rapidly determine the radiated energy and energy magnitude of great shallow earthquakes using teleseismic P-waves.As it usually takes long time to get the information about the source to simulate the corresponding depth of synthetic seismograms,this paper does not consider the influence of focal mechanism in the calculation program,and calculates the green function library of different depths in advance.Such processing can greatly improve the calculation efficiency.Most earthquakes have stable results within half an hour of data,and a few have stable results within an hour.At the same time,the radiated energy E_sand energy magnitude M_e of 115 earthquakes with M_W?6.0 from 2014 to 2019 were calculated by the program,and the seismic catalogue of energy magnitude was provided.At the same time,the calculation results of this paper are compared with the energy magnitude produced by Incorporated Research Institutions for Seismology(IRIS)and produced by The Global Moment Tensor Project Data Center(GCMT)of the Lamont-Doherty Earth Observatory(LDEO)of Columbia University.At the same time,the ratio of radiation energy and GCMT of 25 earthquakes that caused tsunami was compared with 75 earthquakes that did not cause tsunami.At the same time,the energy magnitude,estimated rupture time,and focal mechanism of the earthquake that caused the tsunami were compared with the earthquake that did not cause the tsunami.The main results are as follows:(1)The results measured in this paper are compared with those of IRIS.It can be found from the results that the consistency of the two results is good,with the deviation within 0.2.The results of different focal mechanisms have little difference,while the difference of positive fault earthquakes is the smallest,with the average value of M_e 0.07m.u.greater than that of M_e(IRIS).There are two reasons for the difference between the two results,namely,different energy compensation methods and calculation formulas,and whether the focal mechanism is corrected.While IRIS produces more regular results for the output magnitude,our results are faster and more responsive to rapid response needs while maintaining accuracy and stability.(2)The results measured in this paper are compared with the moment magnitude of GCMT.It can be found from the results that,statistically speaking,the average energy magnitude of earthquakes in the data set is greater than the moment magnitude.Although the moment magnitude of some earthquakes are similar,their energy magnitude results may vary greatly;moment magnitude M_W can only obtain the static characteristics of the source,while the energy magnitude M_e can provide dynamic information of the source and can objectively evaluate the earthquake The damage intensity of the earthquake,therefore,we suggest that the combined use of the two kind of magnitude scales can quickly assess the extent of the disaster caused by larger earthquakes.(3)Compared with earthquakes that did not cause a tsunami,the earthquakes that cause tsunami have the following characteristics:the ratio of radiated energy to seismic moment is low;the energy magnitude is large;the focal depth is mainly concentrated in 20km to 40km;There is a higher proportion of strike-slip earthquakes with more slip components.Earthquakes with the above characteristics have a high tsunami potential.However,some earthquakes that do not have the above-mentioned characteristics also trigger tsunamis,due to the special terrain,submarine landslides,and magnitude factors.The work accomplished in this paper greatly improves the measuring speed of energy magnitude,makes it suitable for rapid reaction system,and enhances the practicability of energy magnitude.The results of this work can provide a reference for future seismic networks to use the energy magnitude as a daily output magnitude to rapidly assess the potential for disasters and tsunamis caused by large earthquakes.