Research!
What do I study?
My research revolves around understanding fault creep along Northern California Faults from a few different approaches:
Using InSAR to map the extent of fault creep in Northern California
Conducting rock mechanic experiments on fault gouge collected from a creeping segment of the Bartlett Springs fault to understand their frictional properties.
Using photogrammetry techniques to document fault creep expressed through offset sidewalks along the Hayward fault
InSAR
Creep on the Maacama Fault in northern California is observed at a few discrete locations, but its overall distribution is poorly constrained. Constraining the extent of fault creep will give insight to seismic hazard assessment in the region. Creep on the faults north of the San Francisco Bay Area have not been observed as extensively as those in the Bay Area due to limited fault-crossing infrastructure and with the land being dominated by vegetation, it causes InSAR to decorrelate. The campaign GPS measurements and the continuous GPS coverage is sparse in the area. The persistent scatterer InSAR (PSI) method can assist in the observation of possible fault creep through the identification of areas with high coherence.
Here (left) are InSAR velocities, using the StaMPS PSI method, processed from a 39 image dataset from ERS-1 and ERS-2, spanning the interval 1992-2000. The aim is to increase the density of surface deformation observations in order to map creep along a segment of the Maacama and the Bartlett Springs Faults.
Rock Mechanics Experiments
Through the collection of fault gouge from Lake Pillsbury along the Bartlett Springs fault, a number of experiments were conducted in order to understand the frictional properties of this fault - which is known to creep in this area.
There is a mixture of antigorite serpentinite, tremolie, chlorite, and talc found in the fault gouge, which is similar to what is found at SAFOD (San Andreas Fault Observatory at Depth). With these different constituents, ternary mixtures were created in order to understand the influence of each of these minerals within the fault gouge.
Structure from Motion (Photogrammetry)
Fault creep is an ongoing process that can damage infrastructure that crosses the fault trace. Expressions of fault creep can be seen through offsets in man-made features such as road markings, fences, walls, sidewalks, and buildings. Of these man-made features, sidewalk offsets become increasingly more noticeable over the years due to fault movement. Since most sidewalk offsets are along public streets, they can easily be recorded photographically for multiple years. Since 2009, we have been measuring the creep rate of the Hayward fault in Fremont, using digital cameras, initially with a tripod set up but then moved to using the Structure from Motion photogrammetric technique in 2015.
Monitoring sidewalk offsets gives us a chance to measure the local creep rate of the Hayward fault and monitor how it is affecting the surrounding urban areas. Here we present creep rate results using photogrammetry as a tool to observe and measure creep from multiple sidewalks along the Hayward fault in Fremont, California.
Bodily Avenue, showing displacements from 2017-2018:
Side profile of the 2 sidewalks showing that one side is aligned and the other side has an offset in alignment (i.e. the distance the sidewalk has moved within a year).
Total displacement of the sidewalk showing movement in the y-axis (horizontal) and z-axis (vertical).
Showing the amount of displacement in the horizontal direction to be 2.5 +/- 0.5 mm/yr.
Showing the amount of displacement in the vertical direction to be 4.5 +/- 0.5 mm/yr.
Sailway Drive, showing 1-year (left) and 2-year (right) displacements:
A 1 year displacement from 2016-2017 implying a creep rate of 2 +/- 1 mm/yr.
A 2 year displacement from 2016-2018 implying a creep rate of 4 +/- 1 mm/yr.