Majority estimates of errors in determining the time in the source and the ratio of the velocities of longitudinal and shear waves according to the Wadati diagram

V.Yu. Burmin

Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia

e-mail: burmin@ifz.ru

Abstract. The article gives upper estimates for errors in determining the time of occurrence of earthquakes (time at the source) ₀ and the ratio of the velocities of longitudinal and transverse seismic waves g propagating from earthquakes. Also considered are cases when the time in the source is considered known and when the ratio of the velocities of the longitudinal and transverse waves is known. The paper draws two main conclusions. The first conclusion is that to determine the time in the outbreak according to the Wadati diagram, it makes sense to fix the slope of the graph. The value of this slope can be defined as the average value of the slopes of the set of graphs as. If we determine the time in the outbreak by plotting the Wadati diagram for each event, determining ₀ and g at the same time, then the errors in determining ₀ and, therefore, in determining the hypocenter can be significant. In the case when the slope of the Wadati diagram is fixed, the accuracy of determining t₀ and, therefore, of the earthquake hypocenters is increased. The second conclusion, which was made in the article, is that the determination of the change in the slope of the Wadati diagram in time for a particular seismically active region becomes very problematic, since the errors in determining the slope of the graph are comparable to the variations of the slope due to changes in the stress state of the elastic medium in the region.

Keywords: Wadati diagram, earthquake hypocenter, hypocenter errors

Funding

This study was performed under State Task of Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences, project no. 0144-2019-0011.

About the author

BURMIN Valery Yurievich – Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences. Russia, 123242, Moscow, Bolshaya Gruzinskaya str. 10, building 1. E-mail: burmin@ifz.ru

Cite this article as: Burmin V.Yu. Majority estimates of errors in determining the time in the source and the ratio of the velocities of longitudinal and shear waves according to the Wadati diagram, Seismicheskie Pribory, 2021, vol. 57, no. 1, pp. 16–28. (in Russian). https://doi.org/10.21455/si2021.1-2

English translation of the article will be published in Seismic Instruments, ISSN: 0747-9239 (Print) 1934-7871 (Online), https://link.springer.com/journal/11990)