Earthquake near DC 3

[bridgebuster]

kawkaz - In the late 90's I went to a conference about the seismic requirements for NYC, and one speaker said exactly what you said about wind loads controlling and un-reinforced masonry buildings being more of a concern.

 

[connect2]

We felt it up here in Ottawa Canada, shook the stuff on desks, paintings hanging on walls rattled, etc ... for about 20 secs, mind you the buildings 'floating' on top of 150 feet of Lake Champlain marine clay then finally bedrock.
Despite all the seismic reinvigoration that's gone on over the last 6 years for us, we're still having the most damage and problems with wind, winds we aren't required to design for but are getting with increased frequency and increased speed.

 

[racookpe1978]

The media is making a "BIG DEAL" about this little earthquake because it happened underneath their very own shaking little bottoms. If the same shaking happened outside of NYC and Washington DC, "they" the national media would not care.

Compare this "evacuation" of federal buildings and mass "leave work early to check on the family" quasi-hysteria in the media to a real 6.0 earthquake in say, Alaska or Washington state or Oregon. Or Peru.

 

[msquared48]

JAE:

It depends on the harmonic it saw, but I agree - I thought of the whiplash effect here, and the fact that the structure is over 120 years old since completed, and 230 years since the conceptual design. Not too many computers back then.

Mike McCann
MMC Engineering

 

[a2mfk]

I'd be WAY more concerned with Irene then a tremor of that magnitude if I lived in the NE right now. Lucky for me it just means I will be doing some surfing here in Florida in the upcoming days...

Mike- as to your point and that other string on seismic design in Florida, I thought about that too. Since the largest seismic event ever in Florida is estimated in the lower "3s", and this one was a 5.8 and did not cause much in the way of serious structural damage in an area with much older structures (that I have seen so far), I would be further convinced our state is just fine in not requiring seismic design since we have 100-150mph wind design requirements...

But who knows, maybe the geophysicists have missed something and we will get a big one in our lifetime!

 

[MiketheEngineer]

We had a about a 4.2 here in St. Louis about two-three years ago at 2:00 am.

Woke my a$$ up. Not my wife.

Told her our bed hadn't moved that much in twenty years!!

I still haven't gotten all the teeth fixed!!

 

[msquared48]

a2mfk:

The thing that worries me about the Florida situation is the proximity geologically to Haiti and what happened there. There are some pretty serious fault lines running east-west there with a long history. That coupled with the fact that we do not know it all, as you said, worries me. Maybe not for a "big one" as we visualize for the west coast, but more than bargained for in Florida for the concrete structures there. That's my concern.

Mike McCann
MMC Engineering

 

[abusementpark]

Mike- as to your point and that other string on seismic design in Florida, I thought about that too. Since the largest seismic event ever in Florida is estimated in the lower "3s", and this one was a 5.8 and did not cause much in the way of serious structural damage in an area with much older structures (that I have seen so far), I would be further convinced our state is just fine in not requiring seismic design since we have 100-150mph wind design requirements...

What was the max earthquake in Florida?

http://earthquake.usgs.gov/earthquakes/states/florida/florida_eq_history.php

The link about doesn't say the magnitudes but the highest on the modified mercalli scale is MMVI, which would correspond to a magnitude of about 4.3.

 

[cap4000]

Here in Northern NJ the PGA was about 1%. At the epicenter it was 30%. We design in NJ for around 40% of PGA. Trains and Tandems rumbling are about 0.5% +/-

 

[JAE]

This link has a photo of the crack on the top area of the Washington monument:

Wash Monument Crack

 

[e104909]

JAE,

is this really true? this seems to be at the top area of the monument. and it seems that the crack was exaggerated.

I was expecting that for a free standing structure the crack should be major at the bottom.

Anyway, I was born in the land where 8-9.0 magnitude is possible.

As observed, for some countries..earthquake magnitude never goes down. year 90's it was magnitude 4-5 only and that is the highest. Nowadays, no more of these magnitude yet this is the lowest.

This must have something to do with the last days.

Regards,
E104909

 

[Teguci]

If they shut down the Washington Monument for that crack they need to start shutting down all the bridges, all the government buildings, all the airports, all the...

My initial response is too many lawyers, but I'd conclude with too much ignorance. There is too much money/prestige to be gained by scaring people and no consequences for false alarms. Land of individualism - the rugged have all left.

 

[HuckleberryFinn]

True Story:

I'm based out of the SE (Carolinas) and my firm had recently finished construction of a large (for this area) 15 story tower for a client in NC. Well, this EQ hits Mineral, VA and our client is suddenly very aware that Earthquakes do, in fact, happen (who knew right?). Anyway, for the past two weeks I've been doing some THA stuff and comparing the Mineral, VA EQ to essentially it's equivalent EQ in NC.

Results? I was actually surprised to find there are some parts of the design response spectrum [ASCE 7-05] that were exceeded by the Mineral, VA EQ. We saw peaks exceed the spectrum for a natural period of .6-.8 seconds and again at 1.1 to 1.3 seconds, the later being much less pronounced(Our data was obtained from the CERI center out of Memphis).

With the realization that more people than just Engineers sit on the Building Codes, anyone got the over/under on the Seismic requirements on the East Coast increasing in the next few code cycles? I know which way I'm betting.

-HF