[IGSMAIL-6357] Magnitude 8.8 earthquake offshore of Japan

Jeff Freymueller jeff.freymueller at gi.alaska.edu
Thu Mar 10 23:45:30 PST 2011


A very large earthquake (M8.8) struck northern Japan about 2 hours  
ago. Details below from the USGS. This is similar in size to the 2010  
Maule earthquake in Chile. Based on the aftershock locations showing  
today, it appears to have involved a roughly 500 km long rupture,  
extending as far south as Tokyo. Check the news for details of damage,  
tsunami, etc. I don't have any information from Japan yet, although I  
have emailed some friends there.

It is likely that this earthquake has caused a significant  
displacement of every GPS site in northern and central Japan, plus  
Korea and parts of northern China. As with the Maule earthquake, it is  
likely that measurable displacements extend as far as several hundred  
km to perhaps more than 1000 km from the rupture zone.

Several IGS08 core sites were certainly or possibly displaced, and  
other sites used by the IGS (such as Usuda and DAEJ) are likely to  
have been displaced.

TSKB  definitely, decimeters to meters
BJFS  maybe mm-cm?
KHAJ maybe mm-cm?
TNML maybe mm-cm?

Non-linear motion with time will almost certainly follow for several  
years or more for sites affected by the earthquake.

IGS centers should look very carefully at solutions and coordinate  
estimates for all sites within a sufficient radius around the  
earthquake rupture before releasing orbit or solution products.

Within a day or so, preliminary slip models from the USGS and other  
sources should be available, based on seismic recordings. For the  
Maule earthquake, these models predicted displacements fairly  
accurately in the far field (hundreds of km from the rupture),  
although they did not work so well for near field. I suspect  
performance will be similar in this case.

Jeff

Begin forwarded message:

> From: ens at usgs.gov (USGS ENS)
> Date: March 10, 2011 9:28:35 PM AKST
> To: jeff at kiska.giseis.alaska.edu
> Subject: 2011-03-11 05:46:23 UPDATED: (M 8.8) NEAR EAST COAST OF  
> HONSHU, JAPAN 38.3 142.4 (dc9d)
> Reply-To: <ens at usgs.gov>
>
>                     == PRELIMINARY EARTHQUAKE REPORT ==
>
> ***This event has been revised.
>
>
> Region:                            NEAR EAST COAST OF HONSHU, JAPAN
> Geographic coordinates:            38.322N, 142.369E
> Magnitude:                        8.8 M
> Depth:                            24 km
> Universal Time (UTC):             11 Mar 2011  05:46:23
> Time near the Epicenter:          11 Mar 2011  14:46:23
> Local standard time in your area: 11 Mar 2011  05:46:23
>
> Location with respect to nearby cities:
> 130 km (81 miles) E (86 degrees) of Sendai, Honshu, Japan
> 179 km (111 miles) ENE (68 degrees) of Fukushima, Honshu, Japan
> 188 km (117 miles) SE (145 degrees) of Morioka, Honshu, Japan
> 376 km (234 miles) NE (37 degrees) of TOKYO, Japan
>
>
> ADDITIONAL EARTHQUAKE PARAMETERS
> ________________________________
> event ID                     :  US c0001xgp
>
> This event has been reviewed by a seismologist at NEIC
> For subsequent updates, maps, and technical information, see:
> http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/usc0001xgp.php
> or
> http://earthquake.usgs.gov/
>
> National Earthquake Information Center
> U.S. Geological Survey
> http://neic.usgs.gov/
>
>
> DISCLAIMER: https://sslearthquake.usgs.gov/ens/help.html? 
> page=help#disclaimer
>
>
> This email was sent to jeff at giseis.alaska.edu
>
> You requested mail for events between -90.0/90.0 latitude and
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Dr. Jeffrey T. Freymueller         Office: 907-474-7286
Geophysical Institute              Fax:    907-474-7290
University of Alaska, Fairbanks    Home:   907-479-3550
PO Box 757320                      Cell:   907-378-7556
Fairbanks, AK 99775-7320           email: jeff.freymueller at gi.alaska.edu
URL: http://www.gps.alaska.edu/jeff/jeff.html

Download Alaska GPS data: ftp://gps.alaska.edu/pub/gpsdata/


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