NO Tsunami threat expected from 6.1 quake in Alaska

6.1 quake just occured in Alaska:


source

Magnitude 6.1
Date-Time Wednesday, September 14, 2011 at 18:10:07 UTC
Wednesday, September 14, 2011 at 09:10:07 AM at epicenter

Location 53.138°N, 173.022°E
Depth 1 km (~0.6 mile) (poorly constrained)
Region NEAR ISLANDS, ALEUTIAN ISLANDS, ALASKA
Distances 27 km (16 miles) NNW of Attu, Alaska
87 km (54 miles) WNW of Shemya Island, Alaska
3180 km (1975 miles) W of WHITEHORSE, Yukon Territory, Canada
3236 km (2010 miles) NE of TOKYO, Japan

Location Uncertainty horizontal +/- 16.8 km (10.4 miles); depth +/- 4.5 km (2.8 miles)
Parameters NST=250, Nph=250, Dmin=85.7 km, Rmss=0.83 sec, Gp=115°,
M-type=regional moment magnitude (Mw), Version=6
Source Magnitude: USGS NEIC (WDCS-D)
Location: USGS NEIC (WDCS-D)

Event ID usc0005ucf

NO tsunami threat expected:

To: U.S. West Coast, Alaska, and British Columbia coastal regions
From: NOAA/NWS/West Coast and Alaska Tsunami Warning Center
Subject: Tsunami Information Statement issued 09/14/2011 at 10:15AM AKDT

At 10:10 AM Alaskan Daylight Time on September 14, an earthquake with preliminary magnitude 6.1 occurred 15 miles/24 Km southwest of Attu I., Alaska .

The magnitude is such that a tsunami IS NOT EXPECTED. However, in coastal areas of intense shaking, locally generated tsunamis can be triggered by underwater landslides. This will be the only WCATWC message issued for this event.

The location and magnitude are based on preliminary information. Further information will be issued by the United States Geological Survey or the appropriate regional seismic network.

source



This really isn't a big deal for this area....just want to head off anyone who may be alarmed by it!

Thanks for being on top of this, WC. Appreciate the info.

reply to post by Open2Truth


You are welcome! I knew it had just happened because of the massive P waves coming across the seismo just off the coast of Washington. here is a screen-shot for fun:

reply to post by westcoast
This is the second 6 plus quake within a week or two.

What is your opinion WestCoast? Are these pressure releases off the end of the Pacific plate where it meets the JuanDeFuca? Maybe I'm thinking of the wrong spot? Could these be big pre-cursor shakes?

Break it down IYO and knowledge base on this part of the shifting planet. Thanks
Red

reply to post by redzareptile


There is always a lot of activity here due to the converging plates...there are also several other faults up there too, as a result of this motion.

I don't really pay a whole lot of attention to that region and haven't studied it much (been concentrating closer to home)....but it is part of the ring of fire, so yes, I always think of larger quakes in that relation.

I typically store these away in my memory to re-examine later if anything else comes up....showing a pattern. Otherwise, I just assume it is part of the normal 'rhythm' there.

reply to post by westcoast


Sweetie, not to be a jerk, but those are S-waves.

P- Primary- arrive first
S- Secondary and/or Sheer- arrive second.

The relationship between P-wave amplitude and S-wave amplitude is interesting. They use this relationship in Japan to predict the likely size of the more damaging S-waves, before the S-waves are even received. Since data off of seismographs is received in chunks or blocks, often the last block only contains the first part, or P-wave when a quake hits, and the rest of the data (the S-wave) you will have to wait for until the next block of data arrives. Those precious seconds in between are valuable.

For example, I constantly monitor the New Madrid. I am just far enough away from it that I have calculated that right about the time I receive the first P-wave from a quake, I will have to make a determination from the P-wave size alone whether to vacate my premises or not. If I see a P-wave come in at 1.2 mm/s, you better believe I am freaking. Cause the S-wave will be a killer.

I'm concerned about its depth... just 1 km? Or is that an error. A 6.1 at 1 km sounds very bad.

reply to post by TrueAmerican


LOL...I could very well be wrong...but that little bit I captured were the very first waves to show. This world of seismo surfing is always a learning experience!