The Creepex-analysis of processes in large earthquakes focal zones by the GIS-ENDDB tools on the Tohoku example

The paper explores the possibility of modifying the creepex (creep and explosion) parameter, an increase in its informativeness and applicability of using public catalogs by the GIS-ENDDB geoinformation system. Instead of the canonical form of the creepex (Cr = MS - kmb - l), the introduced normalized estimate of this parameter is investigated: CrN = 4(MS - mb)/(MS + mb), which has a less pronounced systematic dependence of the difference (MS - mb) on the earthquakes magnitude MS and its significantly lower variance. The catalogs NEIC and ISC are analyzed. An example of this study is carried out on a sample (Jcreepex catalog: 1,458 records) from the ISC Integrated Catalog for the focal zone of the Great East Japanese Earthquake (Tohoku), for 2010-2012, with the ISC own definitions of mb and MS. Based on a complex analysis of the distribution of the creepex-colored earthquake focal zones, patterns of changes in this parameter in space, revealing its connection with the tectonic environment, and in time, revealing patterns of seismogenesis before and after a strong event under consideration, are established. On an example of the crust Tohoku earthquake (March 11, 2011, MS = 8:7) the informativeness of the normalized creepex is confirmed, and it is shown that the source relaxation process partially occurs, by periodic focal chains, with the value of the creepex demonstrating the process alternation of a quasi-plastic flow and a brittle fracture.