Interactive analysis tools for the wide-angle seismic data for crustal structure study (Technical Report)
Gou Fujie 1 5 Junzo Kasahara 2 Kei Murase 3 Kimihiro Mochizuki 4 Yoshiyuki Kaneda 11 Institute for Research on Earth Evolution (IFREE) Japan Agency for Marine-Earth Science and Technology (JAMSTEC) 3173-25, Showa-machi, Kanazawa-ku, Yokohama, Kanagawa 236-0001, Japan.
2 Japan Continental Shelf Survey Co. Ltd., NTC bldg. 3F, 1-11-2 Kyobashi, Chuo-ku, Tokyo 104-0031, Japan.
3 Kawasaki Geological Engineering Co. Ltd., Mita-Kawasaki bldg. 6F, 2-11-15 Mita, Minato-ku, Tokyo 108-8337, Japan.
4 Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-0032, Japan.
5 Corresponding author. Email: fujie@jamstec.go.jp
Exploration Geophysics 39(1) 26-33 https://doi.org/10.1071/EG08006
Submitted: 29 August 2007 Accepted: 13 November 2007 Published: 5 March 2008
Abstract
The analysis of wide-angle seismic reflection and refraction data plays an important role in lithospheric-scale crustal structure study. However, it is extremely difficult to develop an appropriate velocity structure model directly from the observed data, and we have to improve the structure model step by step, because the crustal structure analysis is an intrinsically non-linear problem. There are several subjective processes in wide-angle crustal structure modelling, such as phase identification and trial-and-error forward modelling. Because these subjective processes in wide-angle data analysis reduce the uniqueness and credibility of the resultant models, it is important to reduce subjectivity in the analysis procedure. From this point of view, we describe two software tools, PASTEUP and MODELING, to be used for developing crustal structure models.
PASTEUP is an interactive application that facilitates the plotting of record sections, analysis of wide-angle seismic data, and picking of phases. PASTEUP is equipped with various filters and analysis functions to enhance signal-to-noise ratio and to help phase identification. MODELING is an interactive application for editing velocity models, and ray-tracing. Synthetic traveltimes computed by the MODELING application can be directly compared with the observed waveforms in the PASTEUP application. This reduces subjectivity in crustal structure modelling because traveltime picking, which is one of the most subjective process in the crustal structure analysis, is not required. MODELING can convert an editable layered structure model into two-way traveltimes which can be compared with time-sections of Multi Channel Seismic (MCS) reflection data. Direct comparison between the structure model of wide-angle data with the reflection data will give the model more credibility. In addition, both PASTEUP and MODELING are efficient tools for handling a large dataset. These software tools help us develop more plausible lithospheric-scale structure models using wide-angle seismic data.
Key words: crustal structure, wide-angle reflection data, interactive analysis, traveltime analysis, OBS-airgun, software.
Acknowledgments
We thank many users for their feedback, including bug reports, on our software tools. We use Generic Mapping Tools (GMT) (Wessel and Smith, 1998) inside PASTEUP. Thoughtful comments by the anonymous reviewer improved the manuscript.
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Editor’s Note: This Technical Report has not been peer-reviewed, but is presented as a service to interested members of the exploration geophysics community.