Our research projects span a wide geographic area and address a range of topics within the field of active tectonics.
The Hayward and Calaveras Faults, two strike-slip faults of the San Andreas Fault System passing through the East San Francisco Bay Area and accommodating ~30% of the relative motion between the North American and Pacific plates, are commonly considered independent structures for seismic hazard assessment.
Evaluation of interseismic strain accumulation and creep traditionally relies on GPS, alignment arrays, and creepmeters, providing precise, but spatially sparse measurements. The surprisingly large Mw9.0 Tohoku earthquake ruptured the interface of the subducting Pacific Plate over an approximately 400-km-long and 200-km-wide area and produced a devastating tsunami, on March 11th, 2011. The Mw 7.6 Padang earthquake occurred on 30 September 2009 offshore of central Sumatra (Figure 1).
The fundamental geological structure and rheology of the Tibetan plateau have been debated for decades.
The December 26, 2004 Sumatra-Andaman event was the largest earthquake since the 1960s and the first Mw 9.2 event to occur in the era of modern space geodesy and broadband seismology.
In laboratory experiments, longer stationary contact time leads to larger seismic moment during repeated ruptures.
Currently, there are a number of seismicity analysis techniques that have been used to infer the state of stress within the lithosphere.
We are using campaign and continuous GPS data from the BAVU dataset, as well as stacked ERS1 & ERS2 interferograms to improve our knowledge of the regional deformation field and creep rates on the Central San Andreas fault system.
The Hayward fault is a major strand of the San Andreas fault system accommodating nearly 25% of the deformation across the plate boundary. The most significant earthquake to occur on the Hayward fault in historic times is a M6.8 event in 1868.
We use campaign and continuous GPS measurements as well as InSAR to measure the deformation from slow slip events on the San Andreas Fault.
Understanding the mechanics of the subduction of cold oceanic lithosphere is crucial to the theory of plate tectonics and subduction zone seismogenesis. What determines the timing of earthquake recurrences and their regularity is of fundamental importance in understanding the earthquake cycle and has important implications for earthquake probability and risk estimates. The September 12, 2007 Sumatra Mw 8.4 earthquake initiated 750 km south of the 2005 epicenter.
Along creeping sections of the San Andreas and other faults, small asperities in the fault zone load and fail in characteristic repeating earthquake sequences. To understand the processes and mechanisms driving fault growth and crustal deformation we combine (1) geologic field mapping of offset landforms, (2) Quaternary geochronology to obtain precise estimates of fault slip rates, and (3) distinct element models (DEM) to simulate the behavior and interactions of faults within the southern San Andreas fault system. In May of 2000 the Pillsbury Lake region, a seismically quiescent region bounded by the Ma’acama and Bartlett Springs faults, experienced a burst of seismic activity lasting for six months and culminating in an M4.2 event. New observations of tidal triggering of non-volcanic tremor near Parkfield, CA present a uniqueopportunity to better understand the nature of tremor and the conditions under which it occurs. We first relocated seismicity at the juncture of these two major faults to determine the subsurface seismic structure. The objective of this study is to determine the elastic properties of the lithosphere in Baffin Island Canada by observing and modeling the lithospheric response to the rapid melting of the Barnes ice cap. We use InSAR time-series analysis of ERS, Envisat, and ALOS data to resolve 1992-2011 vertical ground deformation associated with hydrological processes in the Santa Clara Valley, California.
My name is Andreas Viklund, I am 30 years old and work as a professional designer in Jokkmokk, northern Sweden. This is a free website template, which means that you are allowed to use it in any way you want to without any obligations. When the earth shakes in California, the first place you are likely to hear about it is on social media.
A screenshot from the Berkeley Seismological Laboratory shows the MyShake app, released for Android devices on Feb. Now, UC Berkeley scientists are hoping to capture that sharing impulse in a massive science experiment: Using cellphones to detect earthquakes as soon as they start. On Friday, scientists unveiled an app that will test this idea with anyone around the world who wants to participate.
Garrett Perrin and James Riley, both sophomores, are Kappa Sigma fraternity brothers and sophomores at Tulane University. Figure 2: Building tilted due to liquefaction caused by the Niigata, Japan, earthquake in 1964 (From the Karl V. Everybody has probably done it while frolicking at the beach: Stand with both feet on the wet sand and move your body quickly up and down several times without lifting your feet.
How can soil, which is hard enough for you to walk on, lose its strength and stiffness just because it is shaken a little bit? The first time seismologists fully recognized the devastating effects of soil liquefaction was in 1964. Figure 3: Map of liquefaction susceptibility in the San Francisco Bay Area (courtesy of USGS). Below is a list of some of our active and recent projects subdivided into catagories based on the large-scale problem each addresses.
Here we use InSAR to show that surface creep on the Hayward Fault continues 15 km farther south than previously known, revealing new potential for rupture and damage south of the city of Fremont. Here, we use InSAR to resolve interseismic deformation associated with the Hayward and Calaveras Faults, in the East San Francisco Bay Area, with a high spatial resolution. Land GPS stations have recorded up to more than one meter postseismic displacements in two years since the earthquake. Seismicity in the Sumatra region is driven by the oblique subduction of the Indian and Australian plates beneath the Burma forearc block and Sunda plate at the Sunda trench.
We have compiled the most up-to-date velocity field for the Bay Area and use 3-D elastic models to determine the slip rates on Bay Area faults most consistent with our data.
Some of the current questions we hope to answer include: How much of these faults is creeping and how much is locked?

The fault exhibits a diversity of slip behaviors including large coseismic rupture, frequent micro-seismicity, and aseismic creep.
The event nucleated on the southern portion of the fault and ruptured as far north as Berkeley. A series of slip events have been observed (1992, 1996, 1998) using strain- and creep-meters.
The locked zone between the subducting and overriding plates host the planet’s largest earthquakes, including all of the recorded events of moment magnitude 9.0 or larger. This question cannot be answered without statistically sufficient observations of recurrence properties in natural earthquake populations. By calculating their slip based on moment magnitude, they can be used as sub-surface creepmeters. The southern San Andreas fault zone of the SAFS is an ideal structure to investigate and model processes of crustal deformation because a high rate of strain is localized on a relatively simple set of faults, the Mission Creek and Banning faults.
Here we perform a full tidal analysis to determine the stress orientations and magnitudes that favor tremor generation on the lower-crustal San Andreas fault.
Next we identified characteristically repeating earthquakes (CREs) using waveform cross-correlation techniques to investigate how slip at depth is being partitioned in this complex juncture zone. We anticipate a substantial vertical deformation signal is present due to the glaciodynamics associated with Barnes ice cap.
We extract temporally variable deformation patterns embedded in the multi-decadal time series without a-priori constraints using T-mode Principal Component Analysis (TPCA).
If you are interested in more advanced templates or custom design services, don't hesitate to contact me for more information. If you decide to use this template, I kindly ask you to leave the "Original design by Andreas Viklund" link in the footer. They hope that by turning mobile phones into vast data collection points, they can quickly glean information about the quakes and warn those farther away from the epicenter that shaking is on the way. Krystina is now staying at her grandmother's house in Vallejo, while Dante is staying with a family who belongs to her grandmother's church and volunteered to put him up. The overpressure inside the soil causes the sand to squirt out like lava from a volcanic crater. During an earthquake under Niigata in Japan several apartment buildings sank into the ground and tipped over, because the water saturated soil on which they were built liquefied (Figure 2).
The extended trace of the creeping Hayward Fault, also illuminated by shallow repeating micro-earthquakes, documents a surface connection between the Hayward and Calaveras Faults.
Pre-earthquake deformation rates are constrained by nearly 20 years of USGS trilateration measurements and removed from the postseismic measurements prior to the analysis. Viscoelastic relaxation in the upper mantle of the shear stresses induced by the earthquake and aseismic afterslip of the megathrust both contribute to the very rapid crustal deformation observed since the earthquake. The Sunda megathrust has been extremely active ever since the 2004 Mw 9.2 Sumatra-Andaman earthquake, with additional megathrust earthquakes in 2005, 2007, and 2010.
On 12 May, 2008, a Mw 7.9 earthquake occurred on the Longmen Shan that separates the eastern Tibetan plateau and the Sichuan basin. Three months later, it was followed by a second great Mw 8.7 event on an adjoining segment of the subduction zone. The Hayward fault presents an ideal locale in which to test the accuracy of these stress proxies in that we can qualitatively infer the stress along the fault by assuming that fault creep rates are inversely related to stress and thus that stress is high along asperities locked since the 1868 earthquake and low along sections that are accommodating a substantial amount of their slip budget through creep. The project includes abundant field work collecting campaign style GPS data in urban and suburban settings.
No earthquake greater than M4.5 has been observed on the Hayward fault since seismic instrumentation was installed in the early twentieth century. These thrust events have been extensively studied, however a significant portion of subduction zone events are intraplate events, which occur within, rather than along the boundary of, the subducting slab. We are using these virtual creepmeters to examine and compare slip rates on the creeping section of the San Andreas Fault (SAF) and on the associated nearby faults. Furthermore, it is the most poorly understood section of the southern SAFS with respect to slip rate and timing of past large-magnitude earthquakes; therefore, its seismic hazard is difficult to quantify. Previous studies have interpreted this anomalous activity as evidence of magma transport in the crust caused by the northward migration of the Mendocino Triple Junction.
Our results show that extremely small shear stress perturbations primarily influence tremor activity levels while much larger normal stress fluctuations and stressing rates have little to no influence.
CREs are earthquakes with extremely similar waveforms that we believe are caused by repeated slip on the same fault zone patch. In order to observe this signal we plan to assemble multiple interferograms from the regional SAR acquisitions dating from 1991.
The longer-term deformation, which corresponds to poroelastic rebound of the aquifer system following recovery of hydraulic heads after the 1960s low stand, occurs mostly prior to 2000, leading to uplift one order of magnitude smaller than its preceding subsidence. Both hope to find housing locally, as they can't afford to commute across the bridge every day.
Liquefaction occurs only in soils in which the space between individual sand particles is completely filled with water. However, when soil liquefaction occurs under a building, it may sink into the soil, like your feet did during your experiment at the beach. The Bay Area is by no means immune to liquefaction, because many buildings in low lying areas are built on soils saturated with water from the Bay.
At depths greater than 3-5 km, repeating micro-earthquakes located 10 km north-northwest of the surface connection highlight the 3-D wedge geometry of the junction. By implementing an interferogram selection directly based on the spatial coherence, our modified time series approach enables deformation mapping in vegetated areas and leads to refined estimates of along fault-creep rates.
In this research, we integrate the wealth of geodetic data from NE Japan and modeling experiences developed at other margins to investigate the effects of mantle rheology on ollowing the 2011 earthquake. The last remaining section of the Sunda megathrust without a modern great earthquake is the Siberut segment, which lies offshore of Padang.

The earthquake ruptured ~235 km of the Beichuan fault (BCF) and the entire Pengguan fault (PGF). These infrequent events provide the rare opportunity to fundamentally improve our understanding of the earthquake cycle of megathrust ruptures and the constitutive properties of the adjoining oceanic and continental crust and upper mantle. We combine our own data with all known geodetic grade GPS data collected over the last decade by six different agencies. However, paleoseismic data suggest that several large earthquakes have produced surface rupture on both the northern and southern portions of the Hayward fault.
We have made two interferograms spanning the 1998 slow slip event which show significant shallow slip along the central San Andreas.
These intraplate earthquakes are frequent and often damaging events that pose a large seismic hazard to large populations along convergent boundaries across the globe.
Coulomb failure stress models have shown that the 2000 earthquake had a larger impact at the 2007 hypocenter than the 2004 and 2005 earthquakes, and could have contributed to its southern location. Nonetheless, the seismic hazard that it presents is likely to be high since this section of the fault system is the only major section that has not ruptured in historic time. However, a magma intrusion does not fully explain the regional geophysical activity and the spatial seismicity patterns associated with the two swarms. These findings are indicative of near-lithostatic pore pressures in the deep San Andreas fault zone and suggest that low effective normal stresses explain the response of non-volcanic tremor to tidal forcing.
Essentially, our method treats each CRE sequence as a "creepmeter" at depth and derives a slip rate estimate at the location of the earthquake. The magnitude, spatial extent, temporal evolution, and thinning rate estimates can be modeled to constrain the regional elastic properties of the lithosphere surrounding Barnes ice cap. Two patterns of seasonal deformation also exist, both sharply partitioned by the Silver Creek Fault (SCF), the fault being a barrier to across fluid flow. If you want to support my work in some other way than giving credits, there are several ways you can do it. Well, you just simulated one of the most dangerous effects seismic waves can have on buildings: Soil liquefaction.
Our new model of the Hayward and Calaveras Faults argues that they should be treated as a single system with potential for earthquake ruptures generating events with magnitudes significantly greater that 7, posing a higher seismic hazard to the San Francisco Bay Area than previously considered in most assessments. Previous work indicates afterslip dominated in the early (1989-1994) postseismic period, so we model the postseismic viscoelastic relaxation between 1994 and 2010 based on geodetic observations. Thus, it is especially important to understand the fault mechanism of the 2009 Padang earthquake in order to assess how it affects the stress levels on the Siberut segment of the megathrust. Far-reaching deformation and stress transients following these events will impact other faults in the region for decades to come, and either enhance or diminish their likelihood to rupture. When combined using a uniform methodology, we call this new data set "BAVU" (pronounced "Bay View", or the Bay Area Velocity Unification). The difference between the geologic and contemporary creep rates suggests that a slip deficit exists and that the accumulated strain will presumably be released in a future earthquake.
These interferograms allow for the possibility that slip extended further south than inferred from the creep- and strain-meter records. We investigate seismicity changes and GPS-measured velocities, in the 2007 rupture region, for alternative triggering evidence. The question to be addressed in this study is whether this theory is correct, namely, is the seismicity near Pillsbury Lake due to crustal dike propagation?
Additionally, a study of this nature would help to inform the debate on the roles of and interaction between the crust and upper mantle in supporting topographic loads.
We show that by combining this seasonal deformation with hydraulic head data we can characterize basin-wide aquifer system properties and that after callibration, we can accurately estimate water level changes from the observed deformation without well measurements. For more website templates to choose from, check out the sites in the "Sample links" menu to the right. The water exerts pressure on the particles, which in turn determines how tightly they are packed together. We estimate long-term slip rate on these faults by inverting the long-wavelength deformation, and shallow slip due to creep using the short-wavelength deformation. The best fitting result predicts a 11-km-thick viscoelastic lower crust with viscosity of 1019 Pa s below a 19-km-thick elastic upper crust, underlain by a bi-viscous upper mantle with transient viscosity of 10^17 and long-term viscosity of 10^18 Pa s. All of the slip models show oblique thrusting along the SW BCF and a right-slip component gradually increases towards the NE end of the BCF.
We seek as complete an understanding as possible of the processes contributing to this deformation and the resulting stress and seismicity changes throughout southeast Asia. The sub-millimeter scale postseismic may not well resolve the viscosity in different layers, but the inferred lithospheric rheology is consistent with estimation in South California.
The postseismic displacement is a response to the redistribution of stresses induced by the earthquake and can be used to probe the deep rheologic properties underneath the surface (Wang et al., 2012).
Accordingly, the long lapse time since the last surface rupture implies that this section of the SAFS is in the late phase of its earthquake cycle, and that strain accumulated over the past 300 years is likely to be relieved in a large-magnitude earthquake. During the dynamic shaking, however, the water pressure can increase so much that the particles can move freely past each other. Besides, the viscoelastic relaxation may also contribute to the increase of repeating earthquake activity on the San Andreas Fault near San Juan Bautista after the Loma Prieta event. Here we incorporate two-year long geodetic measurements and numerical modeling to examine two end-member hypotheses to provide further evidence to the deep rheology in eastern Tibetan plateau.

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