The rupture process of the 1987 Edgecumbe earthquake, New Zealand

Long-period body-wave modelling of the main shock of the 1987 March 2 Edgecumbe earthquake sequence reveals a multiple rupture event with a moment of 4. 3 × 10 18 N m. The first rupture originated at a depth of about 8 km and propagated to the surface and to the southwest. A second subevent occurred about 3 s later with an epicentre about 9 km to the southwest of the main-shock epicentre. The focal mechanism of the first subevent shows dominantly normal faulting. Comparison with the surface fault break indicates that the northeast-striking, northwest-dipping nodal plane was the fault plane and hence the horizontal slip vector trend was approximately 342°. The second subevent may correspond to the faulting observed on the Te Teko trace.