Publications

Damage to fault-zone rocks during fault slip results in the formation of a channel of low seismic-wave velocities. Within such channels guided seismic waves, denoted by Fg, can propagate. Here we show with core samples, well logs and Fg-waves that such a channel is crossed by the SAFOD (San Andreas Fault Observatory at Depth) borehole at a depth of 2.7 km near Parkfield, California, USA...

The largest historical earthquake in the northern Great Plains occurred on 16 May 1909. Our analysis of intensity assignments places the earthquake location (48.81° N, 105.38° W) close to the Montana–Saskatchewan border with an intensity magnitude MI of 5.3–5.4. Observations from two seismic observatories in Europe give an average Ms value of 5.3. The 1909 earthquake is near an alignment...

No abstract available.

Strong aftershocks following major earthquakes present significant challenges for infrastructure recovery as well as for emergency rescue efforts. A tragic instance of this is the 22 February 2011 Mw 6.3 Christchurch aftershock in New Zealand, which caused more than 100 deaths while the 2010 Mw 7.1 Canterbury mainshock did not cause a single fatality (Figure 1). Therefore, substantial...

The influence of noise in strong-motion records is most problematic at low and high frequencies where the signal to noise ratio is commonly low compared to that in the mid-spectrum. The impact of low-frequency noise (

Using a suite of five hypothetical finite-fault rupture models, we test the ability of long-period (T>2.0 s) ground-motion simulations of scenario earthquakes to produce waveforms throughout southern California consistent with those recorded during the 4 April 2010 Mw 7.2 El Mayor-Cucapah earthquake. The hypothetical ruptures are generated using the methodology proposed by Graves and...

No abstract available

Static Coulomb stress changes imparted by the February 21, 2008 Wells, Nevada earthquake are calculated, using an 8 x 6 km rectangular patch with a uniform slip as a source fault. Stress changes are resolved on nearby active faults using their rake, dip, and strike direction, assuming a fault friction of 0.4. The largest Coulomb stress increase (0.2 bars) imparted to surrounding major...

Within the last decade, advances in the acquisition, processing and transmission of data from real-time seismic monitoring systems has contributed to the growth in the number structures instrumented with such systems. An equally important factor for such growth can be attributed to the demands by stakeholders to find rapid answers to important questions related to the functionality (or...

No strong motion records are available for the 12 January 2010 M7.0 Haiti earthquake. We use aftershock recordings as well as detailed considerations of damage to estimate the severity and distribution of mainshock shaking in Port-au-Prince. Relative to ground motions at a hard - rock reference site, peak accelerations are amplified by a factor of approximately 2 at sites on low-lying...

Using Global Positioning System (GPS) data from permanent sites and U.S. Geological Survey (USGS) campaign data we have estimated co-seismic displacements and secular background crustal deformation patterns associated with the 21 February 2008 Wells Nevada earthquake. Estimated displacements at nearby permanent GPS sites ELKO (84 km distant) and GOSH (81 km distant) are 1.0±0.2 mm and 1...

Despite obvious limitations as a proxy for site amplification, the use of time-averaged shear-wave velocity over the top 30m (Vs30) is useful and widely practiced, most notably through its use as an explanatory variable in ground motion prediction equations (and thus hazard maps and ShakeMaps, among other applications). Local, regional, and global Vs30 maps thus have diverse and...