Earthquake in a maze: compressional rupture branching during the 2012 Mw 8.6 Sumatra earthquake

Lingsen Meng, Jean-Paul Ampuero, Joann M. Stock, Zacharie Duputel, Yingdi Luo, & Victor C. Tsai

Published 2012, SCEC Contribution #1656

Seismological observations of the 2012 moment magnitude 8.6 Sumatra earthquake reveal
unprecedented complexity of dynamic rupture. The surprisingly large magnitude results from the
combination of deep extent, high stress drop, and rupture of multiple faults. Back-projection
source imaging indicates that the rupture occurs on distinct planes in an orthogonal conjugate
fault system, with relatively slow rupture speed. The east-southeast–west-northwest
ruptures add a new dimension to the seismotectonics of the Wharton Basin, which was
previously thought to be controlled by north-south strike-slip faulting. The rupture turns
twice into the compressive quadrant, against the preferred branching direction predicted by
dynamic Coulomb stress calculations. Orthogonal faulting and compressional branching indicate
that rupture is controlled by a pressure-insensitive strength of the deep oceanic lithosphere.

Citation
Meng, L., Ampuero, J., Stock, J. M., Duputel, Z., Luo, Y., & Tsai, V. C. (2012). Earthquake in a maze: compressional rupture branching during the 2012 Mw 8.6 Sumatra earthquake. Science,. doi: 10.1126/science.1224030.