Principal Slip Zone determination in the Wenchuan earthquake Fault Scientific Drilling project-hole 1: considering the B
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RESEARCH ARTICLE - SOLID EARTH SCIENCES
Principal Slip Zone determination in the Wenchuan earthquake Fault Scientific Drilling project‑hole 1: considering the Bayesian discriminant function Sinan Fang1,2 · Zhansong Zhang1,2 · Zhi Wang3 · Heping Pan4 · Ting Du2 Received: 20 March 2020 / Accepted: 1 October 2020 © Institute of Geophysics, Polish Academy of Sciences & Polish Academy of Sciences 2020
Abstract Accurate determination of the Principal Slip Zone (PSZ) of earthquake fault zones is a key task of earthquake Fault Scientific Drilling for future earthquake control. The fault zone structure of Wenchuan earthquake is complex, and there are many strong earthquakes recorded on the fault zone, which make determining the PSZ in the Wenchuan earthquake Fault Scientific Drilling project-hole 1 (WFSD-1) difficult. At present, core analysis of whole coring is the decisive method for determining PSZ depth, and the fresh fault gouge at 589.2 m is the PSZ in WFSD-1. Abundant and comprehensive logging data can only be used as evidence to judge the PSZ. Based on the discrimination function and hyperplane equation in Bayesian discriminant classification, we derive a new algorithm for computing the PSZ possibility using a Bayesian Discrimination function (PSZP-BDF) based on the simplified model, and set up a mode to determine the PSZ directly using machine learning of well logging. For the verification of WFSD-1, the fault gouges are successfully identified and the PSZ depth is accurately located. The algorithm objectively learns the sample data, which is naturally adaptive to the region. The calculation procedure is simple and does not require expensive coring data or heavy core tests in the well. The calculation speed is fast, using multiple physical data types. The PSZP-BDF algorithm is suitable for processing and interpreting earthquake fault scientific drilling data. Keywords Wenchuan earthquake Fault Scientific Drilling (WFSD) · Principal Slip Zone (PSZ) · Bayesian discrimination · Logging
Introduction Weak dynamic seismic stress waves from distant earthquakes are proved to abruptly change the states of many natural geological systems include permeability(Xue et al. 2013; Weaver et al. 2019), liquefaction (Wang 2007), a * Sinan Fang [email protected] 1
Key Laboratory of Exploration Technologies for Oil and Gas Resources, Ministry of Education, Yangtze University, Wuhan, China
2
College of Geophysics and Petroleum Resources, Yangtze University, Wuhan, China
3
Electronics and Information School, Yangtze University, Jingzhou, China
4
Institute of Geophysics and Geomatics, China University of Geosciences, Wuhan, China
sudden increase of seismicity and the dynamic triggering of earthquakes (Peng et al. 2011). Therefore, the theory that the transient seismic-wave pressure in a fluid-filled fracture could increase more than 2 orders of magnitude may be a key technology for artificially controlling earthquakes(Zheng 2018), which requires first predicting the Principal Slip Zone (PSZ) location for the next
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