Research

The earthquake physics group at CERI investigates the mechanisms of seismic events across many scales from centimeter-size lab-quakes to kilometer-size natural and induced earthquakes.

We employ numerical models, experiments and empirical observation to understand earthquake source processes, induced seismicity, fluid flow and fault hydrology. We use advanced seismic processing methods and machine learning to accurately detect and characterize seismicity in nature. The fundamentals of underlying physical processes are explored within our newly developed rock-mechanics lab that combines state-of-the-art seismic and optical imaging. More details about personnel and projects can be found below (students and postdocs highlighted in bold font).

Current projects include:
  • Characterisizing induced seismicity in hydrocarbon basins and geothermal reservoirs in North America and Europe
  • Measurements and numerical models that constrain fault hydrology and poroelastic stresses
  • Source parameters analysis of micro and macro seismicity (M-8 to M4)
  • Coupling between fault structure and seismicity statistics
  • Laboratory observations of preparatory processes before failure

Research Topics

Induced Seismicity



Project Members at U. of M.

Roshan Koirala
Erin Cunningham
Ryan Williamson
Shima Azizzadeh Roodpish
Pranav Appani

Collaborators

Emily Brodsky, UC Santa Cruz
Huiyun Guo, UC Santa Cruz
Pablo Ampuero, Caltech
Egil Hauksson, Caltech

Funded By

U. S. Department of Energy
Southern California Earthquake Center

The considerable increase in seismicity in central Europe and the central U.S. in recent years has brought much attention to the issue of fluid-injection induced seismicity. Although the detailed mechanisms of this sudden increase are far from clear, the general correlation between increased wastewater injection and seismicity clearly suggest an anthropogenic contribution to the earthquakes. A less-discussed, but equally important issue is the lack of conspicuous induced seismicity in hydrocarbon reservoirs, in California. Injection rates and pressures alone are not a good diagnostic tool for induced earthquakes as many wells are not associated with seismicity. This project focuses on detecting and characterizing induced seismicity in California hydrocarbon basins, modeling induced seismicity mechanisms in Oklahoma and finding underlying causes for deep and distant earthquakes from injection wells.

Earthquake source parameters



Collaborators

Aglaja Blanke, GFZ-Potsdam
Grzegorz Kwiatek, GFZ-Potsdam
Egill Hauksson, Caltech
Pablo Ampuero, Caltech
Andreas Plesch, Harvard
John Shaw, Harvard

Funded By

Southern California Earthquake Center
German Research Center for Geosciences (GFZ-Potsdam)

A key parameter in engineering seismology and earthquake physics is seismic stress drop, which provides an estimate of the relative amount of high-frequency energy radiation at the source. We analyze differences in spatial distributions of earthquake source parameters (such as stress drop, corner frequency and seismic moment) to identify significant variations due to crustal heterogeneity in southern California. Moreover, we examine source parameter scaling relations in lab-experiment on faults with different roughness and stress conditions. The dependence of stress drop on crustal conditions and fault roughness implies that stress drops of both small and large- magnitude earthquakes should be affected similarly, resulting in generally more high-frequency seismic energy radiation. Large ruptures and high stress drops are of prime interest in engineering seismology and should be considered in ground motion prediction.

Fault-structure and micro-seismicity statistics



Collaborators

Zirou Jin, University of Wisconsin
Hiroki Sone, University of Wisconsin
Georg Dresen, GFZ-Potsdam
Grzegorz Kwiatek, GFZ-Potsdam
Danijel Schorlemmer, GFZ-Potsdam
Thorsten Becker, UT-Austin

Funded By

German Research Center for Geosciences (GFZ-Potsdam)
German Humboldt Foundation

A major concern in seismological research is the seismic hazard due to large-magnitude earthquakes. While such earthquakes are easily recorded by modern geodetic and seismic instrumentation, they are also rare, providing only a snapshot of long-term crustal deformation. Accumulating tectonic and induced strains are expressed in greater detail in frequently occurring micro-earthquakes (i.e. earthquakes too small to be felt). These small events provide much insight into fault structure, slip and hydrology as well as triggering processes at seismogenic depth where other geophysical data are scarce. Previous and ongoing project focus on the study of fault structure and micro-seismicity statistics in lab and nature to document elastic strain build-up and release.

Fluid flow and poroelastic stresses



Collaborators

K-Won Chang, Sandia National Laboratories
Emily Brodsky, UC Santa Cruz

Funded By

U.S. Department of Energy
German Humboldt Foundation

Fluid injection, from hydraulic fracturing to CO2 sequestration, can lead to fault slip and earthquakes. The mechanisms that cause induced events are complex, involving direct effects within the pressure-affected volume and elastic stress changes at larger distances. Both pressure and elastic stress effects have been well documented in individual cases. However, the relative significance of these effects for the total seismic moment released during injection operations remains to be understood. One component in determining the relative importance of different triggering mechanisms for induced events are more robust constraints on crustal hydrology. In addition, we explore the role of poroelastic stress changes in inducing deep and distant earthquakes. Elastic deformation of shallow reservoirs can induce stresses at large depths so that earthquakes may occur on faults hydraulically isolated from the injection zone.

Earthquake precursors and preparatory processes before failure



Collaborators

Georg Dresen, GFZ-Potsdam
Marco Bohnhoff, GFZ-Potsdam
Grzegorz Kwiatek, GFZ-Potsdam
Yehuda Ben-Zion, USC

Funded By

United States Geological Survey

German Research Center for Geosciences (GFZ-Potsdam)

The recent revival of laboratory seismology, fueled by the availability of faster data acquisition systems and miniature broadband arrays, facilitated detailed seismological observations of micro-fracture and slip processes. These observations suggest that processes governing natural fault slip are also active in laboratory experiments. We document preparatory processes leading to failure using high-rate seismic and mechanical records and test the influence of pore-fluids, damage and fault roughness in amplifying or suppressing precursory signals before failure.

Seismic event triggering and aftershock studies



project members at U. of M.

Kiran Pandey

Collaborators

Joern Davidsen, University of Calgary
Georg Dresen, GFZ-Potsdam
Grzegorz Kwiatek, GFZ-Potsdam

Funded By

German Research Center for Geosciences (GFZ-Potsdam)

What determines if an earthquake occurs in isolation or triggers a cascade of aftershocks? The answer to this questions has significant implications for seismic hazard assessment, because the majority of earthquakes are triggered events. Several processes have been suggested to explain aftershocks, including static stress transfer, pressure diffusion and dynamic ground shaking. Interestingly, in triaxial compression tests on intact and faulted samples, triggered events are rare although other similarities to natural seismicity are prevalent. Our group tests physical mechanisms that govern the presence or absence of triggering in lab and nature using state-of-the-art statistical tests.