The identification and criteria of short-term seismicity gap before a great earthquake

Based on the background of the medium term seismic gap, and the creep rate slow down after accelerated strain release, by using a method of gradually reducing the step length and the window length of scanning, the characteristics and criteria of a short term seismic gap have been studied from multi dimension space research. A new method for identifying a short term gap from 3 D axial stability collation has been advanced. Through the study of 26 earthquake examples in north and south west region of China, we found that a short term seismicity gap appeared in 9～16 months before a strong earthquake, this type of gap is different from the seismogenic gap, and will lasted 4～7 months, end at the time of 3～8 months before the mainshock . The ending is marked by the appearance of a significant earthquake in or near the gap (Sun and Cao, 1995) and of small earthquake in the gap.

Function S-rough sets and law identification

By introducing element equivalence class that proposes dynamic characteristic into Pawlak Z rough sets theory, the first author of this paper improved Pawlak Z rough sets and put forward S-rough sets （singular rough sets）. S-rough sets are defined by element equivalence class that proposes dynamic characteristic. S-rough sets have dynamic characteristic. By introducing the function equivalence class （law equivalence class） that proposes dynamic characteristic into S-rough sets, the first author improved S-rough sets and put forward function S-rough sets （function singular rough sets）. Function S-rough sets have dynamic characteristic and law characteristic, and a function is a law. By using function S-rough sets, this paper presents law identification, law identification theorem, and law identification criterion and applications. Function S-rough sets are a new research direction of rough sets theory, and it is also a new tool to the research of system law identification.