Abstract
AbstractThe crustal structure beneath southwest Japan is investigated through waveform modellings of four local crustal earthquakes by using the generalized ray theory. High-quality seismograms recorded by the Hi-net seismic network are used. The focal mechanism solutions of the events used are estimated by using the firstP-wave polarity data. Twenty-nine paths are used to characterize the crustal waveguide in SW Japan. Optimal 1-D velocity models for different paths are derived individually by waveform modelling. Synthetic tests are conducted to study the effects of different model parameters and to confirm the focal mechanism solutions. Modelling the waveforms individually is proven applicable for the heterogeneous regions. The resulted synthetics match the observed seismograms well. Considerable variations of the Conrad and Moho depths are found in the study area. The Conrad depth ranges from 14.8 to 19.7 km, and the Moho depth ranges from 28.4 to 33.4 km. Considerable variations in the crustal structure are found for the eastern portion of the study area where Biwa Lake lies. The effects of Biwa Lake on different paths are examined in detail.
Highlights
Waveform modelling has become one of the most powerful tools for studying the Earth structure
Waveform Modelling for Crustal Structure Using the estimated source parameters, we examine the crustal model through the search for the maximum correlations over the parameter spaces of the velocity model
We describe the different paths in detail with the corresponding waveform modelling results and the resulted velocity models. 6.1 Event 1 paths
Summary
Waveform modelling has become one of the most powerful tools for studying the Earth structure. Langston and Helmberger, 1975; Dreger and Helmberger, 1993; Zhao and Helmberger, 1994; Zhu and Helmberger, 1996) These studies have demonstrated that an adequate crustal velocity model which generates the recorded characteristics of regional waveforms can be used to retrieve the source parameters of earthquakes. Local and regional waveform modellings play an important role in studying the detailed crust and upper mantle structure. These waveforms are generally complicated due to the great influence of crust heterogeneities. This gives rise to additional reflected and converted body wave phases at short periods (Dreger and Helmberger, 1993)
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