Below is an alternate interpretation from USGS to what I have been posting, suggesting quakes were on the NNE-SSW planes. But, this was sent only a couple hours after the quake. There is still nothing on IRIS or SCEC.

I'll stick with my WNW-ESE parallel faults until I am shown otherwise.

Chris

Date: April 11, 2012 4:31:52 AM PDT
To: ******************
Subject: Mw 8.6 Off the West Coast of Northern Sumatra, INDONESIA and Aftershock

Version Notes:
There was an error in formatting of the Origin Time, which has
been corrected in this version of the Executive Summary
A preliminary Mw8.2 aftershock has been reported by NEIC at
2012/04/11 10:43:09 UTC, this event is SSW of the Mw8.6

NEIC Event Executive Summary

Version #2

PRELIMINARY EARTHQUAKE INFO

Mw 8.6 Off the West Coast of Northern Sumatra, INDONESIA
Wednesday, April 11, 2012 08:38:37 UTC
Wednesday, April 11, 2012 14:38:37 UTC at epicenter

Latitude: 2.311 Longitude: 93.063 Depth: 22 Km

Nearest Cities
438 km (272 miles) SW of Banda Aceh, Sumatra, Indonesia
553 km (344 miles) SW of Lhokseumawe, Sumatra, Indonesia
1793 km (1113 miles) WNW of JAKARTA, Java, Indonesia
3358 km (2086 miles) SSE of NEW DELHI, Delhi, India

USGS Event Links
http://earthquake.usgs.gov/earthquakes/eventpage/usc000905e#summary
http://earthquake.usgs.gov/earthquakes/eventpage/usc00090da#summary

EARTHQUAKE SUMMARY

Talking Points
Similar in location and style of faulting to a M7.2 strike-slip earthquake
on January 10, 2012
The tectonic fabric in the region is from old seafloor spreading, which
would have imprinted an approximately N-S linear trend (fracture zone)
The relative plate motions between Indo-Australia and Sunda/Asia is NNE,
so slip could be compatible with the NNE fault plane
For all practical purposes this is an intra-plate earthquake

SEISMOTECTONIC INFORMATION

Tectonic Summary
The M8.6 April 11, 2012 earthquake off the west coast of northern Sumatra,
Indonesia, occurred as a result of strike-slip faulting within the oceanic
lithosphere of the Indo-Australia plate. The quake was located
approximately 100 km to the southwest of the major subduction zone that
defines the plate boundary between the Indo-Australia and Sunda plates
offshore Sumatra. At this location, the Indo-Australia plate moves
north-northeast with respect to the Sunda plate at a velocity of
approximately 52 mm/yr.
Large strike-slip earthquakes, while rare, are not unprecedented in this
region of the Indo-Australian plate. Since the massive M 9.1 earthquake
that ruptured a 1300 km long segment of the Sumatran megathrust plate
boundary in December of 2004, three large strike-slip events have occurred
within 50 km of the April 11, 2012 even. These earthquakes occurred on
April 19 2006 (Mw6.2), October 4 2007 (Mw6.2) and January 10, 2012
(Mw7.2). In all three cases, the style of faulting was similar. These
events align approximately with fabric of the sea floor in the diffuse
boundary zone between the Indian and Australian plates.

EARTHQUAKE EFFECTS

Prompt Assessment of Earthquakes for Response
http://earthquake.usgs.gov/earthquakes/eventpage/usc000905e#pager

Damage Reports
No major damage reported

DYFI Link
http://earthquake.usgs.gov/earthquakes/eventpage/usc000905e#dyfi

EARTHQUAKE SOURCE PARAMETERS

Style of Faulting: Strike-Slip

Wphase Moment Tensor
12/ 4/11 8:38:38.00

Epicenter: 2.348 93.072
MW 8.6

USGS/WPHASE CENTROID MOMENT TENSOR
12/ 4/11 8:38:38.00
Centroid: 2.248 92.872
Depth 25 No. of sta:109
Moment Tensor; Scale 10**21 Nm
Mrr= 1.25 Mtt=-5.99
Mpp= 4.74 Mrt= 1.34
Mrp=-0.63 Mtp=-7.03
Principal axes:
T Val= 8.40 Plg= 9 Azm= 63
N = 1.14 79 271
P = -9.54 4 154

Best Double Couple:Mo=9.0*10**21
NP1:Strike=199 Dip=80 Slip= 3
NP2: 108 87 170

MEDIA INFORMATION

Links to News Articles
http://www.msnbc.msn.com/id/47013639

http://www.newscientist.com/article/dn21686-magnitude-86-earthquake-strikes-off-sumatra.html

CONTACT INFORMATION