Ventura Fault Mesh

Recent and Ongoing Research Projects

Scott T. Marshall :: Department of Geology :: Appalachian State University

My collaborators, students, and I work to better understand the mechanics of fractures in the Earth and how we can measure deformation of the Earth's surface at seismically active plate boundaries with modern satellite geodetic techniques. Our recent and ongoing research primarily focuses on:

  1. How can we quantify and map out crustal deformation using GPS and InSAR data?
    • How does surface deformation vary with time?
    • Which surface motions are due to tectonics & earthquakes, and which are seasonal or anthropogenic?
    • How can satellite geodesy be used to accurately locate and characterize active faults?

  2. How do earthquake-generating faults accommodate tectonic deformation?
    • How does slip vary across a fault surface in three dimensions?
    • How do faults interact with each other?
    • How can physics-based fault models be used to constrain earthquake hazards?
To learn more about this work, click on any of the images or "learn more" links below.

3D Interactive Models of Active Faults in Southern California

Many people incorrectly think that the San Andreas is the main earthquake source in southern California. The truth is that the San Andreas is not the only game in town. There probably hundreds of active faults in southern California, many of which may pose a significant seismic hazard to population centers. The Southern California Earthquake Center (SCEC) has compiled a vast amount of geologic and geophysical data into an open source geometric representation of southern California faults called the Community Fault Model (CFM). Here, I provide interactive 3D PDF representations of various regions of the CFM that have been carefully re-meshed for numerical stability in most matrix inversions. Even if you don't care about matrix inversions, it is still pretty cool to see the 3D fault structure in southern California. Learn more...

Geodetic Measurement of Crustal Deformation in the Western Transverse Ranges, CA

Ventura InSAR

Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data can be used to measure motions of the surface of the Earth at the sub millimeter scale. With these advanced modern techniques, we can now quantify spatial and temporal variations in strain, seasonal deformation, and anthropogenic deformation. Once all non-tectonic motions have been characterized, we can mathematically remove them and the complex tectonic deformation patterns emerge. Learn more...

3D Mechanical Models of Active Faulting in the Ventura Basin, CA

Oak Ridge Fault

The Ventura basin contains a thick sequence of Pliocene sediments (up to 18 km thick!) formed by active faulting along a complex network of oblique reverse faults. Recent work has suggested that this region may be capable of a ~M8 earthquake similar to the 2008 M7.9 Sichuan earthquake. To accurately assess seismic hazards in this region, we need to know which faults are most dangerous and which ones are likely less active. The first step, is to determine the distribution of slip rates on the regional faults...a job for 3D Mechanical models. Learn more...

3D Mechanical Models of Active Faulting in Los Angeles Basin, CA

Hollywood Fault

Much of my recent research has focused on creating 3D mechanical models of the tectonically-complex Los Angeles Basin of southern California. Results of these models generally agree quite well with interseismic GPS data, geologic fault slip rates, folding patterns. Furthermore, because many of the faults in greater Los Angeles buried and do the reach the surface of the Earth (e.g. 1994 M6.7 Northridge, 1987 M5.9 Whittier Narrows), mechanical models offer a practical way to understand fault behavior where traditional geologic study is not possible. Learn more...

Miocene Faulting in Southeast Nevada

Nevada Faulting

Even the shallowest earthquakes nucleate at depths > 1 km, so we typically can't directly observe earthquake-related processes and the complex fault structures responsible for these events. What we can do is observe exhumed ancient fault systems that were once active and try to understand their structure and behavior. Once such fault system that I have worked on is the Lake Mead fault system, located just east of Las Vegas, Nevada. Here, both field mapping and mechanical modeling evidence suggests that strike-slip and normal faults are genetically related, and a regional-scale west-dipping detachment is likely present at depth. Learn more...

Fracturing on Jupiter's Icy Moon, Europa

Europa's Cycloids

Diurnal tidal forces (from Jupiter) have resulted in a highly fractured surface on Jupiter's moon, Europa. Fractures follow the same physical laws whether on Earth or other planetary bodies, so we can use the principles of fracture mechanics to understand fractures on other planetary bodies. Curved cracks, called cycloids, or flexi, are unique to the surface of Europa and may form due to a combination of opening, shearing, and secondary fracturing due to diurnal tidal forces. We have also documented several examples of previously unrecognized strike-slip faulting and secondary fracturing on Europa's heavily fractured icy surface. Learn more...