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 do subduction zone fault systems interact in space and time? How do these fault systems and associated deformation regulate subduction zone evolution and structure?

  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

Noel Bartlow                University of Kansas

Susan Beck                   University of Arizona
Magali Billen                UC Davis

*Emily Brodsky             UC Santa Cruz

*Roland Burgmann      UC Berkley

*Eric Dunham               Stanford University

William Frank               MIT

*Melodie French         Rice University

Alice Gabriel                LMU Munich/UC San Diego

Thorne Lay                   UC Santa Cruz

Jeff McGuire                US Geological Survey

Samer Naif                   LDEO/GeorgiaTech

*Andrew Newman       Georgia Tech

Summer Ohlendorf     NOAA/National Tsunami Warning Center

Christine Regalla         Northern Arizona University

Demian Saffer              UTIG

*Donna Shillington      Northern Arizona University

*Harold Tobin               University of Washington

Daniel Viete                  Johns Hopkins University
*Doug Wiens                Washington University

Rob Witter                    US Geological Survey

* Steering Committee Member

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

Interest Group Contacts

Donna Shillington - Donna.Shillington (at) nau.edu
Melodie French - mefrench (at) rice.edu