Faulting and Earthquake Cycles

When and Where Do Large Earthquakes Happen?

How Do Faults Work – at all Levels of the Subduction System?

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Anticipating the timing of major earthquakes and which fault segments present the greatest hazard has long been a challenge in subduction zone science. At the largest spatial scale, deformation throughout the subduction system is coupled in space and time, and novel geodetic and seismologic observations made possible by the emergence of offshore instrumentation is poised to help us unravel these connections. At the smallest spatial scale, deformation processes control how rocks respond to the boundary conditions, whether by faulting or distributed flow, and how faults slip, whether by seismogenic slip, aseismic creep, or intermediate behaviors.


Understanding these processes requires new laboratory experiments designed to determine the properties of complex rocks that experience complex histories and investigations of rocks exhumed from fossil systems to ground-truth these measurements and observations. Finally, relating the processes by which rocks deform locally to the spatial and temporal evolution of the system requires numerical models validated by structural images from active source seismic, MT, bathymetric data, and modern surface techniques (LiDAR, paleoseismology). The focus of this interest group is to design integrated SZ4D experiments and efforts to address the questions of when and where earthquakes happen in subduction zones.

Overarching question: Which subduction zone segments are more likely to produce big earthquakes and what properties govern that likelihood?


  1. How are subduction system evolution and structure regulated by the upper plate, outer rise, and slab faulting and associated deformation?

  2. What controls the speed and mode of slip in space and time?

  3. Does distinctive precursory slip or distinctive foreshocks exist before earthquakes? What causes either foreshocks or precursory slip?

  4. Under what physical conditions and by what processes will rapid slip during an earthquake displace the seafloor and increase the likelihood of generating a significant tsunami?

Working Group Members

Geoff Abers            Cornell

Noel Bartlow           U. Kansas

Susan Beck              U. Arizona
Magali Billen           UC Davis

*Emily Brodsky        UCSC

*Roland Burgmann UC Berkley

Eric Dunham            Stanford

William Frank          MIT

*Melodie French     Rice

Alice Gabriel           LMU Munich/UCSD

Thorne Lay              UCSC

Jeff McGuire           USGS

Samer Naif              LDEO/GaTech

*Andrew Newman  Georgia Tech

Christine Regalla    Northern Arizona U.

Demian Saffer         UTIG

*Donna Shillington Northern Arizona U.

*Harold Tobin          U. Washington

Daniel Viete            JHU
Doug Wiens          Washington U.

Rob Witter              USGS

* Steering Committee Member

June 2020 Webinar
Planning for the SZ4D Initiative: Meet the Faulting & Earthquake Cycles Working Group

Interest Group Contacts:

Emily Brodsky - brodsky@ucsc.edu

Donna Shillington - Donna.Shillington@nau.edu
Melodie French - mefrench@rice.edu