Forward waveform modelling procedure for 1-D crustal velocity structure and its application to the southern Korean Peninsula

Abstract

S U M M A R YWe propose a full-grid search procedure for broad-band waveform modelling to determine a 1-D crustal velocity model. The velocity model can be more constrained because of the use of broad-band waveforms instead of traveltimes for the crustal phases, although only a small number of event-station pairs were employed. Despite the time-consuming nature of the full-grid search method to search the whole model parameter space, the use of an empirical relationship between the P-and S-wave velocities can significantly reduce computation time. The proposed method was applied to a case in the southern Korean Peninsula. Broad-band waveforms obtained from two inland earthquakes that occurred on 2007 January 20 (M w 4.6) and 2004 April 26 (M w 3.6) were used to test the method. The three-layers over halfspace crustal velocity model of the P-and S-wave velocities was estimated. Comparisons of waveform fitness between the final model and previously published models demonstrate advancements in the average value of waveform fitness for the inland earthquakes. In addition, 1-D velocity models were determined for three distinct tectonic regions, namely, the Gyonggi Massif, the Okcheon Belt and the Gyeongsang Basin, which are all located inside the study area. A comparison between the three models demonstrates that the crustal thickness of the southern Korean Peninsula increases from NW to SE and that the lower crustal composition of the Okcheon belt differs from that of the other tectonic regions.

Spatio-temporal evolution of a dispersed magmatic system and its implications for volcano growth, Jeju Island Volcanic Field, Korea

“…Proterozoic granulite and amphibolite complexes form part of the lower crust in the Korean peninsula (Lee and Cho, 2003). The basement of Jeju Island is considered to be a continuation of the Okcheon Belt in the Korean Peninsula (Kim et al, 2002), which formed during the Paleozoic (Cluzel et al, 1990) and is modeled to be underplated lower crust (Kim et al, 2011). The boundaries between lower to middle and middle to upper crust are at c. 22 and 8km depth respectively, and the base of the crust is at c. 33km depth (Kim et al, 2011).…”

“…The basement of Jeju Island is considered to be a continuation of the Okcheon Belt in the Korean Peninsula (Kim et al, 2002), which formed during the Paleozoic (Cluzel et al, 1990) and is modeled to be underplated lower crust (Kim et al, 2011). The boundaries between lower to middle and middle to upper crust are at c. 22 and 8km depth respectively, and the base of the crust is at c. 33km depth (Kim et al, 2011). Comparative isotope data for the underplated crust are not available, however, lower crustal granulite in the Sino-Korean Craton has 143 Nd/ 144 Nd c. 0.5108 to 0.5114, much lower than Jeju basalts, but with comparable 87 Sr/ 86 Sr ( 87 Sr/ 86 Sr 0.7040-0.7071; Huang et al, 2004;Fig.…”

The 2016 Gyeongju earthquake sequence revisited: aftershock interactions within a complex fault system

“…A regional 1-D velocity model for the Gyeongsang Basin (e.g. Kim et al 2011) was applied throughout the hypocentre determination.…”

“…The same regional one-dimensional velocity model used in the location procedure (e.g. Kim et al 2011) was used to construct Green's functions as well.…”

Measurement of seismometer orientation using the tangential P-wave receiver function based on harmonic decomposition

“…Since we stack the R-and T-RFs over a 5 • interval in backazimuth, the size of randomly selected data matrices in bootstrapping is no more than 64 × M. Ambiguity between the ϕ min and ϕ min + 180 • can be resolved by choosing an orientation that yields a positive polarity of a constant harmonic term in the R-RF. Kim et al (2011). The north is towards the right.…”