Lockloss most likely caused by ground motion:
https://ldas-jobs.ligo-wa.caltech.edu/~lockloss/index.cgi?event=1370555148

Peakmon plots attached.
There was no Earthquake warning just a sudden Lockloss. The Seismic foms showed a sharp but small increase which pointed me in the direction of looking for Seismic info. There was a sudden increase in H1:ISI-GND_STS_ITMY_Z_BLRMS_30M_100M and other Z axis BLRMS.
I am surprised that the Lockloss Analysis tool didn't tag it as an Earthquake.