The study of earthquake source properties inform our understanding of the physics that govern slip on faults and the hazards associated with large earthquakes. My work in this field uses large seismic arrays to image the spatiotemporal evolution of seismic energy release during large earthquakes to estimate detailed variations in rupture properties such as rupture direction and speed. Below are results from two recent megathrust earthquakes: the February 27, 2010 Mw 8.8 Maule, Chile earthquake (Figure 1) and the March 11, 2011 Mw 9.0 Tohoku, Japan earthquake (Figure 2).
2010 Mw 8.8 Chile Earthquake
Figure 1: (Left) The February 27, 2010 megathrust earthquake was recorded by the Transportable Array (red triangles) in the United States. This data are filtered to high frequencies (1-5 Hz) in order to image detailed earthquake source properties. (Right) Energy release as a function of time (upper left corner) for this event. Warm and cold colors represent high and low amplitude energy release, respectively. The black star is the epicenter of the event and the black line is the coastline of Chile. This event involved a dominant northern rupture at speeds around 2.9 km/s. A lower amplitude southern rupture can also be observed around 70 seconds after the epicentral time.
2011 Mw 9.0 Japan Earthquake
Figure 2: (Left) Transportable Array station locations during the March 11, 2011 earthquake. Recorded data are filtered between 0.8 and 2 Hz. (Right) Energy release from the Mw 9.0 Tohoku event. The red star is the epicenter, the white line is the coastline of Japan, and the yellow line is the Japan trench. Time (UTC) is shown in the upper right corner. This event exhibited four different rupture directions and speeds.