Earthquakes not just a West Coast Problem

[Stormsfury]

Some may know that the Eastern U.S. also has earthquakes as well, but many don't ....

Charleston, SC on August 31st, 1886 was the location of the Strongest East of the Mississippi River U.S. earthquake of record.

The New Madrid Quake in Missouri was even stronger.

This is a map of East Coast Earthquakes and their locations from 1973-2000 - quite a maxima near Charleston, SC, and in Tennessee. However, as seen on this map, every state pictured here has had earthquakes.

More details on my website - Earthquake Information Opened

[isobar]

Storms, Have you been able to feel any of the earthquakes in SC?

[mf_dolphin]

Anyone else notice how a lot of the quake lines form either along rivers or parallel to them? Guess we have some clue as to what formed the paths of some of them

Just thought that was interesting...

[JQ Public]

Yeh people around g-boro and winston salem often have a few small tremors each year!

[isobar]

The New Madrid, MO quake in 1812 holds the record for the strongest in the continental US with a 7.9. Actually it's tied for 1st place w/Ft. Tejon, CA.

I hope we don't see that again in our lifetime.

[Stormsfury]

Storms, Have you been able to feel any of the earthquakes in SC?

Yes I have felt and heard several of the earthquakes ...
Ironically, the one most recent ... 4.32 magnitude quake on November 11, 2002 - I did not feel nor hear (this was offshore about 30 miles of CHS) -

The last one I felt and heard occurred while I was at work back in January 2002 - I heard an explosion indicative of an earthquake, when two of my co-workers had that bewildered look ... I said it sounded like an earthquake, in which 2 days later, I found out that I was right.

The quake back on Aug. 21st, 1992 was rated a 4.4 on the Richter Scale near Summerville ... that one, I heard 2 separate explosions within 7 seconds - immediately during the second explosion, everything shook and rolled quite vigorously ... I was eating a pizza and sitting in this very spot, when immediately I knew what was happening, and I jumped out of the chair into the doorway and ducked down. Turned out the epicenter of this quake was only a couple of miles away, about 6 miles deep. The quake lasted 22 seconds.

[Stormsfury]

Anyone else notice how a lot of the quake lines form either along rivers or parallel to them? Guess we have some clue as to what formed the paths of some of them

Just thought that was interesting...

Quirky, isn't it? This seems typical of East Coast Mid-Continental Faults.

[Stormsfury]

The New Madrid, MO quake in 1812 holds the record for the strongest in the continental US with a 7.9. Actually it's tied for 1st place w/Ft. Tejon, CA.

I hope we don't see that again in our lifetime.

Depending on the Source - The New Madrid Earthquake(s) actually there were a series of them in a 3 to 4 month span - The largest one there could have been as high as 8.8 - however, this source rates it as an 8.1, another one 8.0, and another at 7.8 - This ranks 1st, 2nd, and 4th on the Largest Contiguous U.S., with Fort Tejon, CA at 3rd (7.9)

Charleston, SC ranks 11 on the U.S.G.S. (United States Geological Survey) at a 7.3 ...

I placed the link of this list here.
http://wwwneic.cr.usgs.gov/neis/eqlists/10maps_usa.html

[2 Seam Fastball]

Parts of my area here in Westchester County Southeastern NY had very mild earthquakes recently. They weren't much to feel but one was i think a 1.5 and a 4 on the richter scale. They said that a bigger one could come soon.

[breeze]

The New Madrid quakes occured from December 1811 - February 1812.
The strongest quake, in Feb. 1812, created a 13,000 acre lake now
known as Reelfoot Lake, in Tiptonville, TN, out of what was once a
small cypress swamp! Seems nature just did a little rearranging with
the landscape there...

[Aslkahuna]

is estimated to be in the same magnitude range as the Fort Tejon and New Madrid shocks. This temblor rattled much of SE AZ as well and had major effects upon the flow of the San Pedro River. The shock originated 30 miles south of Douglas AZ near the intersection of the San Bernardino Fault that extends north into AZ and an unnamed fault that extends NW along the SW face of the Huachuca Mountains, along the fault controlled Canelo Hills and into the Santa Ritas-significant ground movement and disturbances were noted in this area. Tucson was strongly shaken as was Tombstone. A repeat today would hit a much higher population (and many more towns and cities) much of which has no experience with earthquakes (I was born in CA and lived 8 years in the Philippines so I'm quite familiar with them).

Steve

[Stormsfury]

February 26th, 2003 - 4:42 am - 2.12 tremor on the Middleton Fault
February 28th, 2003 - 2:02 am - 2.58 tremor on the Middleton Fault

The first of the year was a 2.12 tremor on the Middleton Fault at 1:49 am on February 1st, 2003.

[Stormsfury]

A little late update.

Another tremor occurred on March 2nd, 2003 (Sunday) at 12:18 pm EST.
So far, this was the strongest tremor of the year near 2.9 magnitude.

[streetsoldier]

As I type this, I am sitting just above the New Madrid fault line; the last "shakeup" here was centered about 23 miles SSW of this location, at a 4.3...felt like we were on a roller-coaster for about 30 seconds!

Add that the soil here is primarily silt and sand (as this was once swampland, reclaimed betweeen 1870 and 1940, not dissimilar to the Dutch "polders" in Lake Ijssel), and you can see the fate that awaits us should we have a "big blow" such as the 1811-12 event. :o

[isobar]

streetsoldier, I heard that an earthquake on soft sediments like that can last up to 3 times longer than on bedrock. Not good news for your area.

[Aslkahuna]

but the soft sediments can also transmit damaging vibrations over longer distances which is one reason why eastern US earthquakes are felt over larger areas than the corresponding earthquakes in the West.

Steve

[streetsoldier]

What really gives me the "willies" is that the earth here can liquefy very easily; the water table is always high, and the least underground disturbance can, and did, change the course of the Mississippi River (pre-1811-12, it ran west of here by about 15-20 miles).

And yes, tremors in silty areas do have a much longer duration and affect greater distances than those in CA, or wherever the fault line is surrounded by bedrock or mountainous terrain.

[Aslkahuna]

is also a problem in coastal areas as well and is a particular problem in parts of San Francisco down by the Bay (the Marina District) along the East Bay shore line and other parts of the West Coast and in Japan.

Steve

[M2]

Liquefaction is also a problem in coastal areas as well and is a particular problem in parts of San Francisco down by the Bay (the Marina District) along the East Bay shore line and other parts of the West Coast and in Japan.

Steve

When a long-duration quake occurs of a higher magnitude within an area of silty unconsolidated soils and a water source, liquifaction can result. The amplified quake waves cause a centrifuge effect that separates out the strata from the water; the denser material sinks low, the particles of sand and silt also fall with gravity and the water moves to the top - this all in any given area. The total effect is like a parfait: heavier denser stuff at the bottom, medium-weight materials in the middle topped off by a column of H20 - instant flood. Areas around shorelines are the most at risk; the Embarcadaro in San Francisco, Pier 39 etc. are all sitting on unconsolidated soils and *fill* - which is the kiss of destruction in a high-magnitude quake. Those multi-million dollar properties, brightly painted buildings, tourist attractions, eateries, jazz clubs, chocolate factory would collapse when their foundations would disappear and sink. It would be interesting to analyze how their insurance companies performed a risk assessment to grant them policy coverage. :Fade-color

[gator]

Parts of my area here in Westchester County Southeastern NY had very mild earthquakes recently. They weren't much to feel but one was i think a 1.5 and a 4 on the richter scale. They said that a bigger one could come soon.

NY certainly is not free from the grips of seismic activity! The northern areas of the state experience minor tremors several times a year, with shocks in the 4.0-6.0 range happening once every 5 years or so... the most recent of which occurred this past summer with it's epicenter at AuSable Valley (aproximately 250 miles north of NYC). The force from this quake was felt as far north as Montreal and Ottawa.

- gator.