J. H. Dieterich

Modeling Injection‐Induced Seismicity with the Physics‐Based Earthquake Simulator RSQSim

Although the phenomenon of earthquakes induced by the subsurface injection of fluids has been recognized, and the basic mechanisms understood, for many decades (e.g., Healy etxa0al. , 1968), the recent increase in seismicity associated with oil and gas development, including large damaging events (e.g., Ellsworth, 2013; Keranen etxa0al. , 2013; Hough, 2014; Rubinstein etxa0al. , 2014) makes clear the need to better understand the processes controlling such seismicity and to develop techniques to mitigate the associated seismic hazard.nnThe relationship of fault stress, fault strength, and fluid pressure at the onset of fault slip in the most basic form is given by the modified Coulomb criterion, ![Graphic][1] (1)in which τ and σ are the shear and normal stress, respectively, acting on the fault surface, P is the pore‐fluid pressure, and μ is the coefficient of fault friction. The term ( σ − P ) is the effective normal stress (Terzaghi, 1925). From equationxa0(1), a fault can be brought to a critical state through an increase of shear stress τ , a decrease of the normal stress σ , an increase of fluid pressure P , or some combination of the three. Increase of pore‐fluid pressure is the most widely cited cause of earthquakes induced by human activities (National Research Council, 2012). Consequently, investigations and models of induced seismicity have tended to focus mainly on spatial changes of fluid pressures (Hsieh and Bredehoeft, 1981; Shapiro and Dinske, 2009).nnAlthough the immediate cause of injection‐induced earthquakes is the increase of fluid pressure that brings a fault to a critical stress state, models of the spatial changes of fluid pressure alone are insufficient to either predict or understand the space–time characteristics of induced earthquakes. Comprehensive system‐level models that couple physics‐based simulations of seismicity with reservoir simulations of fluid …nn [1]: /embed/inline-graphic-1.gif

Visual Exploration and Analysis of Time Series Earthquake Data

Earthquake hazard estimation requires systematic investigation of past records as well as fundamental processes that cause the quake. However, detailed long-term records of earthquakes at all scales (magnitude, space and time) are not available. Hence a synthetic method based on first principals could be employed to generate such records to bridge this critical gap of missing data. RSQSim is such a simulator that generates seismic event catalogs for several thousand years at various scales. This synthetic catalog contains rich detail about the earthquake events and associated properties. Exploring this data is of vital importance to validate the simulator as well as to identify features of interest such as quake time histories, conduct analyses such as calculating mean recurrence interval of events on each fault section. This work1 describes and demonstrates a prototype web based visual tool that enables domain scientists and students explore this rich dataset, as well as discusses refinement and streamlining of data management and analysis that is less error prone and scalable.