GRACE CMT Solutions

I've been a great admirer of GRACE since the first time I 'met her'. That was at a meeting in Potsdam, Germany, a beautiful city just outside (on the 'wrong side' = old Eastern Germany) Berlin. I was attending a geodesy meeting, I do not even remember exactly which one, when we popped in to listen to Chris Reigber, one of the pioneers in space-based gravity measurements, giving a talk thanking the community for a reward he had just gotten for his work in this field. GRACE is the brainchild of Chris Reigber and his group at Geoforschungzentrum in Potsdam, and NASA. One of the remarkable things about GRACE is that she over performs, all the time, again and again.

I've been a great admirer of GRACE since the first time I 'met her'.
That was at a meeting in Potsdam, Germany, a beautiful city just outside
(on the 'wrong side' = old Eastern Germany) Berlin. I was attending a
geodesy meeting, I do not even remember exactly which one, when we
popped in to listen to Chris Reigber, one of the pioneers in space-based
gravity measurements, giving a talk thanking the community for a reward
he had just gotten for his work in this field.

GRACE is the
brainchild of Chris Reigber and his group at Geoforschungzentrum in
Potsdam, and NASA. One of the remarkable things about GRACE is that she
over performs, all the time, again and again.

Shin-Chan Han
works at NASA and has looked at GRACE looking at Tohoku. He found
astonishing facts. GRACE can namely see the earthquake over a longer
period of time so that we get the accumulated magnitude of the
earthquake. The plates continue to move after the quake and that is
added up in terms of energy and then magnitude.

Independently
from seismic and GPS ‘displacement’ data analysis, GRACE finds the CMT
source depth within the lower crust and further delineates a group of
earthquake CMT parameters; increasing dipping angles (7 – 16° ± 2°) and,
simultaneously, decreasing moment magnitudes (Mw 9.17 – 9.02 ± 0.04)
with increasing source depths from 15 to 24 km within the lower crust.

GRACE
CMT solutions indicate the averaged earthquake moment over a month
including postseismic effects (~10% of coseimic moment).

Large
negative anomalies (-5 to -20 microGal) were observed in the back-arc
region of the thrust faults after the 2004 Sumatra-Andaman IS.
(Mw9.2-9.3), 2010 Maule, Chile (Mw8.7-8.8), and 2011 Tohoku-Oki
earthquake (Mw9.0-9.1). They consistently indicate dilatation in the
crust after the ruptures. (ocean reduces offshore positive anomalies and
is not the ‘cause’ of negative anomalies)

The enhanced
instrumentation such as laser tracking (from GRACE FO, GRACE-II) would
be helpful to explore the smaller and more frequent seismic events (~Mw
7.5-8).

Old NID

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