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Originally posted by this_is_who_we_are
reply to post by kennvideo
No.worries. I was just putting my 2 cents in. What are the chances of another big one in the same area any time soon? That may be a stupid question, but I just had to ask. I know little about earthquakes and plate tectonics and the like.
Originally posted by muzzy
No use rushing in and plotting a bunch of early estimates for these, I like to give it at least 24 hrs before the first map, that way you get some idea where the aftershocks are headed
Did a quick map for El Salvador 7.4 aftershocks yesterday for EQR, did 72 hours worth, used EMSC data this time. Haven't done the Network locations or history yet for that one.
27/08/2012 offshore Central America 7.4 aftershocks
but heres Utsu's in the meantime, nothing in that spot, so a fresh rupture (since 2003 and 6+ anyway)
1987-06-06T18:40:29.470Z, 10.713, 126.051, 6.5 Mw, 17km
Twitter Inc., the microblogging service that lets more than 140 million users send short messages on everything from the mundane to the life-altering, tipped off the U.S. Geological Survey to the 7.6-magnitude earthquake that hit near the coast of the Philippines today.
The Reston, Virginia-based agency detected tweets about the earthquake one minute and seven seconds after the seismic event, which occurred at about 8:47 p.m. local time, Paul Earle, a USGS seismologist, said in a telephone interview.
The USGS occasionally receives false alarms from its prototype system, such as when Twitter users post messages about the song “Earthquake” by British musician Labrinth.
“It’s not foolproof,” Earle said.
‘Melt welt’ mechanism of extreme weakening of gabbro at seismic slip rates
* Kevin M. Brown
* Yuri Fialko
Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093, USA
Nature 488, 638–641 (30 August 2012) | doi:10.1038/nature11370
Received 14 December 2011 | Accepted 29 June 2012 | Published online 29 August 2012
Laboratory studies of frictional properties of rocks at slip velocities approaching the seismic range (~0.1–1 m s−1), and at moderate normal stresses (1–10 MPa), have revealed a complex evolution of the dynamic shear strength, with at least two phases of weakening separated by strengthening at the onset of wholesale melting1, 2, 3, 4. The second post-melting weakening phase is governed by viscous properties of the melt layer and is reasonably well understood5, 6. The initial phase of extreme weakening, however, remains a subject of much debate. Here we show that the initial weakening of gabbro is associated with the formation of hotspots and macroscopic streaks of melt (‘melt welts’), which partially unload the rest of the slip interface. Melt welts begin to form when the average rate of frictional heating exceeds 0.1–0.4 MW m−2, while the average temperature of the shear zone is well below the solidus (250–450 °C). Similar heterogeneities in stress and temperature are likely to occur on natural fault surfaces during rapid slip, and to be important for earthquake rupture dynamics.
* Earth sciences
* Materials science