| The determination of seismic energy is an important basic problem in seismic quantification research.It plays an important role in the research of seismic quantification and engineering seismology.The part of the energy released when an earthquake occurs that propagates in the form of seismic waves is called seismic radiation energy.Because it is the only part of the seismic energy that can be measured,the seismic energy we usually mention refers to radiated seismic energy.Energy magnitude is the magnitude determined by radiated seismic energy Es which is the source physical parameter,and since the energy radiated by the earthquake in the form of seismic waves is mainly concentrated near the corner frequency of the source spectrum,the energy magnitude Me is more suitable to describe the potential damage of the earthquake.Especially for shallow strong earthquakes,which are prone to serious disasters,it is very important to measure the radiated seismic energy and energy magnitude in time.In this paper,the research on the influence of focal mechanism on the estimation of radiated seismic energy is carried out.Using the broadband teleseismic P-wave waveform data of the Global Seismic Network and China Earthquake Digital Network,the Es and Me on the focal mechanism corrections and not of 105 shallow earthquakes with Mw≥6.0 from 2014 to 2019 were measured.Analyze the influence of focal mechanism on the estimation of radiated seismic energy and energy magnitude,and compare it with the energy magnitude Me produced by IRIS and the moment magnitude Mw measured by GCMT.Discuss the reliability of the energy magnitude produced in this paper and the necessity of adding focal mechanism correction,and the joint measurement of energy magnitude Me and moment magnitude Mw is of great significance for earthquake disaster assessment and earthquake emergency response.The specific results are as follows:1)The focal mechanism has a significant impact on the radiated seismic energy,and the influence of different types of focal mechanisms on the radiated seismic energy varies greatly.The strike-slip fault has the greatest impact on the radiated seismic energy,with an average impact of 0.34 on the energy magnitude;The influence of normal fault is the second,and the average impact on the energy magnitude is 0.08;the thrust fault has the smallest impact,and the average impact on the energy magnitude is 0.05,and the near-vertical strike-slip fault has the greatest impact.2)The differential magnitude ΔM(ΔM=Me-Mw)of the earthquake with different focal mechanism are also different,with strike-slip faults of 0.31,normal faults of 0.21 and thrust faults of 0.08,which indicates that the radiated seismic energy efficiency of the strike-slip faults is higher,followed by normal faults and the lowest thrust faults.The energy magnitude Me and the moment magnitude Mw reflect the dynamic and static properties of the earthquake source,respectively.It is of great significance to jointly measure the energy magnitude Me and the moment magnitude Mw for the reasonable assessment of earthquake disaster and earthquake emergency response.3)Compared with the energy magnitude produced by IRIS,our measured results have little difference,and the absolute value of the overall average difference is within 0.2.For normal faults,our results are 0.15 larger on average,for thrust faults,0.09 larger,and for strike-slip faults,0.19 larger.4)The focal mechanism of the Ludian earthquake on August 3,2014,shows that it belongs to strike slip type,with a nearly vertical fault layer.Ludian earthquake’s radiated seismic energy is 2.07×1014 J,energy magnitude Me is 6.6,moment magnitude Mw(GCMT)is 6.2.And its energymoment ratio(ratio of radiant energy Es to seismic moment Mo)is 9.74×10-5,slow parameter is-4.01,both above the global average level.Therefore,although the magnitude of the earthquake was not large,it caused serious damage to ground buildings and casualties. |
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