My research focus is observational seismology. I use recordings of seismic waves to understand how earthquakes work and to quantify the hazards they pose. My research group is working to develop a better understanding of earthquake scaling, and it's implications for the physics of the earthquake source, and the intensity of strong ground motion. We continue to work on new methods to study tectonic tremor. More recently we have undertaken studies of intermediate-depth earthquakes to understand their mechanism and how it might differ from shallow earthquakes. My research group is also developing improvements to the estimation of Green's function from the ambient seismic field, and using them to construct "virtual earthquakes" that can be used to predict variations in the strength of shaking in real earthquakes.