| 英文摘要: | The researchers have developed sophisticated numericals models that explore how faults that produce earthquakes, large and small, also produce movements that are slow, and look different from typical earthquakes. Earthquakes are typically generated by rapid slip on pre-existing faults inside the Earth, loaded by tectonic plate motion. Observations show that the rapid slip, with the average velocity of the order of 1 m/s, coexists with much slower slip that can be measured, e.g. using GPS. These types of phenomena often exist in the same place and can influence each other. This project will look to simulate several cycles of large earthquakes and, by incorporating what we know about how the Earth deforms, the physics of seismic waves and faults, observe how slow events and both small and large earthquakes work. They will take their simulations and compare them with observations made in experimental labs and in nature. The studies will lead to better understanding of earthquake nucleation, fault properties, and the predictive value of foreshocks sequences, and hence help mitigate seismic hazard. Combined with codes for wave propagation and site and building response, the methodology for simulating slow slip and earthquake sequences can become a vital ingredient of physics-based simulation capability for seismic hazard analysis This kind of modeling could have transformative impacts on our understanding of earthquakes and their hazards. These types of models add another tool to our study of hazards.
To study the interaction of slow slip with seismicity-producing fault patches, the researchers will use a unique numerical approach capable of resolving all stages of slip: accelerating slip during earthquake nucleation, dynamic rupture with all inertial (wave) effects, postseismic slip, and interseismic slip including transients. Slow slip will be generated as a part of long-term fault simulations using several physical mechanisms to enable comparison between them: (i) nucleation processes on faults governed by standard velocity-weakening rate-and-state friction, (ii) modifications of such processes due to inelastic shear dilatancy, and (iii) slow slip on velocity-strengthening faults. The fault models will include one or multiple patches defined as areas of different frictional properties. Several types of differences that may lead to seismicity will be explored, including variations in effective normal stress, rate-weakening properties, dilatancy, and permeability. The focus here is on simulating and characterizing well-resolved interactions of slow slip and seismic events in terms of their radiated spectra, stress drops, potential for seismicity recurrence on a patch during a single episode of slow slip, spatial extent of the generated events in relation to the patch sizes, modification of slow slip by the resulting seismicity and its postseismic effects, and the consequences of interaction between nearby patches. Comparison of these features with observations (including laboratory studies) will allow identification of scenarios relevant to the observed phenomena as well as clarify the nature of heterogeneity on natural and laboratory faults. The developed detailed models of slow slip interaction with heterogeneous patches will be used to create simplified representations of microseismicity for use in future simulations of earthquakes and slow slip, including foreshock sequences and tremor, in realistic fault settings. |