Microseismic monitoring technique and its applications at coal mines: present status and future prospects

The microseismic (MS) monitoring technique, which uses the signals emitted during the coal or rock fracture process to study the mechanical stability of coal or rock material and/or the associated rock structure, is a real time, dynamic, and continuous geophysics monitoring method.This technique mainly includes MS sensors network optimization, MS events recognition and arrival time picking, velocity model, MS waves characteristics, source location and tomography, focal mechanism, and MS monitoring and early warning, etc.During the past 30 years, MS monitoring technique has been widely used in the coal mines safety and efficient production.A lot of research achievements on MS wave characteristics during the coal or rock fracture process, source location, MS activities laws, MS monitoring and early warning of rockbursts have been obtained.The preliminary studies and discussions have been carried out on the MS monitoring of coal and gas outbursts, water inrush, coal or rock hydraulic fracture, and underground coal mines rescue.Some useful research results have been obtained.However, there are still many scientific issues about coal mine MS technology needing to research systematically and in-depth, which mainly include the MS waves characteristics of different coal or rock fracture types, especially for those fractures with fluid participated in; high accuracy MS events automatic recognition and arrival time picking methods; the passive seismic tomography theory and techniques based on MS technology; the precursor information intelligence and multi-information fusion monitoring and early warning system for coal or rock dynamic disasters; coal or rock hydraulic fracturing MS monitoring and imaging technique.In the meantime, the high performance, high precision, high reliability of MS monitoring system with independent intellectual property rights should be developed and improved.