Identification of the meta-instable stress state and study of its mechanism and evolution of relevant physical fields would be of great significance for determination of potential seismic risks and estimation of criti...Identification of the meta-instable stress state and study of its mechanism and evolution of relevant physical fields would be of great significance for determination of potential seismic risks and estimation of critical times. In laboratory experiments, that the specimen enters the meta-instable is marked by accelerated stress release. Could we use the experimental result to identify the earthquake in natural conditions? Because the observational data from one station can only reflect the stress state beneath this station, the key problem for identification of the meta-instability is how to recognize regional stress state through observational data from many stations. In this work, we choose the evolution of the temperature field over varied deformation stages during a stick-slip event on a 5 bending fault as an example, and attempt to find the response features of the physical quantity when the fault enters the meta-instable state. We discuss the characteristics of stages for the stress build-up, stress-time process deviating from linearity before instability, meta-instability, instability, and post-instability, respectively. The result shows that the fault instability slide is a conversion process from independent activities of each fault segment to synergism activity. The instability implies completion of the synergism. The stage deviating from linearity is the onset of stress release, and it is also the onset of the synergism. At the meta-instability stages, stress release becomes dominant, while the synergism tends to finish. Therefore, the analysis of the regional overall stress state should not start from individual stations, and instead it should begin with the evolution of the whole deformation field.展开更多
Relocation result shows that the aftershocks of the Lushan MS7.0 earthquake spatially distribute in a shape like"half bowl",indicating that the rupture structure of the mainshock is a highly curved surface.K...Relocation result shows that the aftershocks of the Lushan MS7.0 earthquake spatially distribute in a shape like"half bowl",indicating that the rupture structure of the mainshock is a highly curved surface.Kinematic analysis reveals that a laterally varied dislocation pattern occurs on this curved fault even though a single relative horizontal movement controls slip on this fault.Reverse slip prevails on curved fault.However,significant normal slip is predicted near the edge of north flank.Moreover,the north flank features left-lateral slip while the south flank contrarily features right-lateral slip.The relative scope of aftershock distribution implies inadequate breaking of the curved fault during the mainshock,calling for the attention to potential earthquake risk on the neighboring portions of the coseismic rupture due to significant increase of the coseismic Coulomb stress.Coseismic stress modeling also reveals that it is unnecessary for the stress on ruptured part to be unloaded following the earthquakes on the curved fault.The coseismic stress loading on ruptured elements unveils the specialty of faulting for the Lushan earthquake and we conclude that this specialty is due to the highly curved fault geometry.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos. 40872129, 41172180)
文摘Identification of the meta-instable stress state and study of its mechanism and evolution of relevant physical fields would be of great significance for determination of potential seismic risks and estimation of critical times. In laboratory experiments, that the specimen enters the meta-instable is marked by accelerated stress release. Could we use the experimental result to identify the earthquake in natural conditions? Because the observational data from one station can only reflect the stress state beneath this station, the key problem for identification of the meta-instability is how to recognize regional stress state through observational data from many stations. In this work, we choose the evolution of the temperature field over varied deformation stages during a stick-slip event on a 5 bending fault as an example, and attempt to find the response features of the physical quantity when the fault enters the meta-instable state. We discuss the characteristics of stages for the stress build-up, stress-time process deviating from linearity before instability, meta-instability, instability, and post-instability, respectively. The result shows that the fault instability slide is a conversion process from independent activities of each fault segment to synergism activity. The instability implies completion of the synergism. The stage deviating from linearity is the onset of stress release, and it is also the onset of the synergism. At the meta-instability stages, stress release becomes dominant, while the synergism tends to finish. Therefore, the analysis of the regional overall stress state should not start from individual stations, and instead it should begin with the evolution of the whole deformation field.
基金supported by the Fundamental Research Funds for Central Public Welfare Research Institutes(DF-IGCEA-0608-2-18)the Special Fund for China Earthquake Research Project(201008003)
文摘Relocation result shows that the aftershocks of the Lushan MS7.0 earthquake spatially distribute in a shape like"half bowl",indicating that the rupture structure of the mainshock is a highly curved surface.Kinematic analysis reveals that a laterally varied dislocation pattern occurs on this curved fault even though a single relative horizontal movement controls slip on this fault.Reverse slip prevails on curved fault.However,significant normal slip is predicted near the edge of north flank.Moreover,the north flank features left-lateral slip while the south flank contrarily features right-lateral slip.The relative scope of aftershock distribution implies inadequate breaking of the curved fault during the mainshock,calling for the attention to potential earthquake risk on the neighboring portions of the coseismic rupture due to significant increase of the coseismic Coulomb stress.Coseismic stress modeling also reveals that it is unnecessary for the stress on ruptured part to be unloaded following the earthquakes on the curved fault.The coseismic stress loading on ruptured elements unveils the specialty of faulting for the Lushan earthquake and we conclude that this specialty is due to the highly curved fault geometry.
