Rupture Process of the 2011 Tohoku-Oki Earthquake Based upon Joint Source Inversion of Teleseismic and GPS Data

This study investigated 18 broadband teleseismic records and 451 near field GPS coseismic deformation data to determine the spatial and temporal slip distribution of the 2011 Tohoku-Oki earthquake (M 9.0). The results show a large triangular shaped slip zone with several asperities. The largest asperity centered above the hypocenter at about 5 - 30 km depth. A secondary large asperity was found in the deeper subduction zone beneath the hypocenter. The average slip on the fault is similar to 15 m and the maximum displacement on the biggest asperity is > 30 m. The temporal rupture process shows that the slip nucleated near the hypocenter at the beginning, and then ruptured to the shallow fault plane forming the largest asperity. The slip developed in the deeper subduction zone in the second stage. Finally, the rupture propagated toward the north and south of the fault along the Japan Trench. The source time function shows three segments of energy releases with two large peaks related to the development of the asperities. The overall rupture process is similar to 180 seconds. This source model coincides well with the aftershock distribution and provides a first-order information on the source complexity of the earthquake which is crucial for further studies.