Traveltime estimation of first arrivals and later phases using the modified graph method for a crustal structure analysis

서지정보

· 발행기관 : 한국지구물리.물리탐사학회
· 수록지 정보 : 지구물리와 물리탐사 / 12권 / 1호 / 105 ~ 113페이지
· 저자명 : Ryuji Kubota, Eiichiro Nishiyama, Junzo Kasahara, Kei Murase

초록

The interpretation of observed waveform characteristics identified in refraction and wide-angle reflection data
increases confidence in the crustal structure model obtained. When calculating traveltimes and raypaths, wavefront methods
on a regular grid based on graph theory are robust even with complicated structures, but basically compute onlyfirst arrivals. In
this paper, we develop new algorithms to compute traveltimes and raypaths not only for first arrivals, but also for fast and later
reflection arrivals, later refraction arrivals, and converted waves between P and S, using the modified wavefront method based
on slowness network nodes mapped on a multi-layer model. Using the new algorithm, we can interpret reflected arrivals, Pglater
arrivals, strong arrivals appearing behind Pn, triplicated Moho reflected arrivals (PmP) to obtain the shape of the Moho,
and phases involving conversion between P and S. Using two models of an ocean-continent transition zone and an oceanic
ridge or seamount,we show the usefulness of this algorithm, which is confirmed by synthetic seismograms using the2DFinite
Difference Method (2D-FDM). Characteristics of arrivals and raypaths of the two models differ from each other in that using
only first-arrival traveltime data for crustal structure analysis involves risk of erroneous interpretation in the ocean-continent
transition zone, or the region around a ridge or seamount.

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