Research status of earthquake forecasting in hydraulicfracturing induced earthquakes

In the new types of industrial activities including unconventional energy extraction associated with shale gas and hot dry rock,gas reservoir operations,CO2 geological storage,undergoing research on induced earthquake forecasting has become one of the forward positions of current seismology.As for the intense actual demand,the immature research on induced earthquake forecasting has already been applied in pre-assessment of site safety and seismic hazard and risk management.This work will review systematically recent advances in earthquake forecasting induced by hydraulic fracturing during industrial production from four aspects:earthquake occurrence probability,maximum expected magnitude forecasting,seismic risk analysis for engineering and social applications and key scientific problems.In terms of earthquake occurrence probability,we introduce statistical forecasting models such as an improved ETAS and non-stationary ETAS and physical forecasting models such as Seismogenic Index(SI)and hydro-mechanism nucleation.Research on maximum expected magnitude forecasting has experienced four stages of linear relationship with net injection volume of fluid,power exponential relationship and physical forecasting regarding fault parameters.For seismic risk analysis,we focus on probabilistic seismic hazard assessment and quantitative geological susceptibility model.Furthermore,this review is extended to key scientific problems that contain obtaining accurate fault scale and environmental stress state of reservoir,critical physical process of runaway rupture,complex mechanism of fault activation as well as physical mechanism and modeling of trailing effect.This work in understanding induced earthquake forecasting may contribute to unconventional energy development and production,seismic hazard mitigation,emergency management and scientific research as a reference.

Generic preparation and entanglement detection of equal superposition states

Quantum superposition is a fundamental principle of quantum mechanics, so it is not surprising that equal superposition states(ESS) serve as powerful resources for quantum information processing. In this work, we propose a quantum circuit that creates an arbitrary dimensional ESS. The circuit construction is efficient as the number of required elementary gates scales polynomially with the number of required qubits. For experimental realization of the method, we use techniques of nuclear magnetic resonance(NMR). We have succeeded in preparing a 9-dimensional ESS on a 4-qubit NMR quantum register. The full tomography indicates that the fidelity of our prepared state with respect to the ideal 9-dimensional ESS is over 96%. We also prove the prepared state is pseudo-entangled by directly measuring an entanglement witness operator. Our result can be useful for the implementation of those quantum algorithms that require an ESS as an input state.