There is now posted a M5.7 aftershock at 0.19 N, and others to 2.9 N...the one at 4.95 N I would consider an aftershock in the previous rupture zone. So, 2.7 deg of latitude on a NW-SE subduction zone is well over 300 km ...I guess that sounds about right for a M8.7. OK...Harvard nodal plane 1 strikes 329.....so 31 deg west of north....2.7 deg *111 km/deg=299.7 km
299.7 km/(cos(31))=350 km.....I still have to draw a little triangle to do trig....I guess Petra can just plug in the Lat-Longs into the distance formula...

Oh, yeah...on previous post I neglected to point out that the area to the SE that last failed in 1833 has had 28 years extra to accumulate slip compared to what failed today...the subduction rate would be similar...
Chris