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Imaging of the Source Properties of the February 27, 2010, Maule,
Chile Earthquake Using Data from the Transportable Array
Eric Kiser (Harvard University), Miaki Ishii (Harvard University)
The availability of high-quality data from a large, dense network of seismic stations achieved by the Transportable Array component
of the USArray project has proven fruitful in studies of the subsurface structure. These data also provide vital information
for imaging some of the rupture properties of giant earthquakes. The coherent arrivals throughout the array, combined with
time-reversal to potential source locations, converts rich information of the waveform of a particular seismic phase to rupture
propagation and relative energy release. This back-projection approach requires minimal a priori knowledge of the event, and
with near real-time data, such as those from the Transportable Array, the analysis can be performed within the time window
relevant for hazard mitigation, especially for tsunami assessment. The figure below shows an example of the application of the
technique to the Maule, Chile earthquake that occurred on February 27, 2010 (Mw8.8). The Transportable Array was at a teleseismic
distance for an effective P-wave back-projection. The large size of the array provided the necessary range in distance
and azimuth for high resolution of the rupture process, and some details of the event are imaged with little artifacts. The rupture
propagates primarily to the north from the epicentre for a length of 360 km and lasts about 120 seconds, corresponding to
a rupture velocity of about 3.0 km/s. There is also a lower amplitude (relative to northern rupture) signal imaged to the south
of the epicentre which reaches its maximum level at about 80 seconds after the event initiation. The images suggest a bilateral
nature of the earthquake, and that the potential slip distribution is far from uniform, with main energy release located north of
the epicentre occurring in the later part of the 120-second duration.
Back-projection results from the February 27, 2010, Mw8.8, Maule, Chile earthquake. (a) The distribution of TA stations (red triangles). (b) Relative energy release of
the entire earthquake. The white dots are aftershocks. (c) Relative energy release at different times of the rupture.
2010 IRIS Core Programs Proposal | Volume II | Earthquake Source Studies | II-63