Active Tectonics and Geodesy
William Barnhart, Assistant Professor
The University of Iowa

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Research

Earthquakes are fundamental indicators of strain in the lithosphere as well as threats to life and infrastructure in seismically active regions. To better understand earthquakes, we use a suite of observations from ground-based and remotely sensed geodesy (GPS, InSAR, and optical imagery) to characterize the surface displacement fields of earthquakes. We then use these high quality measurements along with inverse methods developed by our research group to map subsurface fault slip, examine the tectonic context of the earthquake, assess potential stress interactions between earthquakes, and look for new and exotic fault slip behaviors.

Rapid Global Earthquake Response

Geodetic and remote sensing imagery increasingly contributes to the rapid, near real-time characterization of disastrous earthquakes. Using many of the techniques we apply to fundamental earthquake research, we work with the U.S. Geological Survey's National Earthquake Information Center to provide timely and accurate information about earthquake source properties that can are included in USGS earthquake response products.

Interferogram and static slip distribution of the 2015 Mw8.3 Coquimbo, Chile earthquake. Interferogram courtesy of insarap.org.

Continental Deformation

In addition to analyzing single earthquakes, we use high resolution radar, optical imagery, and topographic data sets in concert with seismological catalogs to address issues related to regional active tectonics. Topics of research interest include the contributions of fault slip to the development of geological structures, variable fault behavior over multiple seismic cycles, volcanic deformation, and characterization of regional tectonic geomorphology through remotely sensed observations.

Funding Sources:

     National Science Foundation (Award #1645014): Collaborative Research: A joint seismic and geodetic investigation into the structure and

                                                                                    behavior of an intracontinental subduction zone, Nepal

     Southern California Earthquake Center (Award #16147): High-resolution topographic mapping of southern California with optical imagery

     Southern California Earthquake Center (Award #17086): Continued development of high-resolution DEMs of southern California

Tectonics of the Middle East

The Eurasian plate boundary is the most seismically active continental deformation zone in the world. Large, destructive earthquakes span from Greece and the eastern Mediteranean, throughout Turkey, Iran, Iraq, Pakistan, and Afghanistan, and then along the Himalaya Mountains bounding India, Nepal, Tibet, Bhutan, and China. The combination of earthquake shaking in close proximity to humans, rapidly growing populations along this plate boundary, and lagging implementation of earthquake-resistant engineering practices means the Eurasian plate boundary plays host to many of Earth's most devastating earthquakes. Our research in this plate boundary zones focuses on two areas: Improved rapid characterization of disastrous earthquakes to support relief efforts, and analysis of earthquakes, aseismic fault slip, and tectonic geomorphology to unravel the tectonic evolution of the plate boundary

Funding Sources:

         NASA Earth Surface and Interior:  Distributed strain in southern Pakistan: How and why do single faults slip in multiple directions?

         NASA New Investigator Program: Imaging the seismotectonic structure of the Arabia-Eurasia plate boundary: Towards the full integration

                                                               of seismology and space-based geodesy

Human-Induced Seismicity

Induced seismicity, or earthquakes driven by human interactions with the Earth, can come from many sources: oil and gas production, wastewater disposal, hydrofracturing ("fracking"), geothermal energy production, CO2 sequestration, mining, and reservoir impoundment. These earthquakes are mostly small, but several examples in recent years (Oklahoma, Colorado) have shown that induced earthquakes can be both large and destructive. Thus, there is societal need to understand and mitigate this hazard.

 

Our research focuses on integrating a range of observations from InSAR time series analysis, seismology, regional geology, and hydrology to understand the causative relationships between human practices and induced earthquakes.

Funding Sources:

         USGS Earthquake Hazards Program: Characterizing human induced seismicity and deformation through space geodetic methods