BEIJING - A lot of speculation still exists about whether or not the Sichuan earthquake could have been predicted. In fact, a lot of silly rumors are floating around about the earthquake and its connection to natural events that are happening right now in the capital; AKA: The somewhat wet weather we've been encountering in Beijing. (A colleague of mine suggested to me that bad weather happened after the Tangshan earthquake in 1976, so there may be some sort of correlation?!?) So in an effort to debunk these crackpot theories and relay a slight bit of science into the mix, I thought it best to post this notation a friend of mine took at the last meeting of the Foreign Correspondents Club of China.

Speakers:

David Simpson from the Incorporated Research Institutions for
Seismology (IRIS) Consortium

Walter Mooney from US Geological Survey (USGS)

(this is re-written from my notes and not exact quotes)

Q: Can earthquakes be predicted?

A: NO, at least not for short-term earthquakes. But seismologists say
active faults that generate large earthquakes repeat approximately
every 150 years (the last big one in Sichuan along the same fault line
was about 150 years ago). All that can be said is that the last one
happened 150 years ago so area X is due for another one at some point
(although nobody knows exactly when)

Q: Could the Sichuan earthquake have been predicted?

A: No, because like most earthquakes, it didn't have any foreshocks.
To date the two have met with top Chinese earthquake experts and they
say they don't have any data beforehand that indicates they knew an
earthquake of that magnitude would come. The Wenchuan area is not a
highly active area but large earthquakes have been known to happen
there.

Q: Can aftershocks be predicted?

A: According to Bath's law, the largest aftershock is normally 1.2
units smaller than the initial earthquake, so the warnings in Chengdu
that an aftershock of up to 7.0 is statistically possible to predict

Q: How poorly built were the buildings in the known earthquake area?

A: The buildings in the earthquake zone were built to withstand 100
gal, which is equivalent to 1 unit of energy. The earthquake released
five times that. So the engineers did their job but didn't anticipate
an earthquake of this size.

Q: Could the dams in the area cause the earthquake?

A: There is talk of the weight and pressure of the water making it
more earthquake prone, but they think it's not a factor in this
earthquake. They said there are very LIMITED cases where resevoirs led
to earthquakes (but never causing one as large as the one in
Wenchuan). So please help quash this idea that the Three Gorges dam or
resevoirs nearby had something to do with the earthquake.

Q: After the earthquake, some hotels wouldn't let guests stay in rooms
above the 19th floor. Is that a good precaution?

A: The only reason they can come up with why hotels did that is that
in the case of a huge earthquake the elevators won't be working and
people might have to run down more flights of stairs to get outside.
Otherwise they thought it was a strange policy. However it is safe to
assume that the first three levels of a building are not a good place
to be during an earthquake as it will collapse.

Q: Is it fishy that the Chinese boosted the earthquake up to an 8.0?

A: The USGS puts the earthquake at 7.9. An 8.0 earthquake releases 3
times more energy that. The experts say this type of margin of error
is possible in an earthquake this size. However they don't discredit
the fact that sometimes these readings are politically motivated, like
in Lima, Peru when the USGS said the earthquake last year was an 8.0
but the government said it was 7.9 because by law, if there is an
earthquake of 8.0 or higher, the government has to give money to
citizens.

Q: Can animals be trained to predict earthquakes?

A: They wish.


Earthquake basics:

One magnitude 8.0 earthquake happens each year, BUT it isn't common
for that to happen in the middle of a continent like it did in
Sichuan.

Why it happens - earthquakes is a result of energy release due to the
constant circulation of heat within the earth.

Epicentre - when we talk about the epicentre, we have to think of it
as a crack on the earth's crust rather than a tiny point on a map.
Think of it as throwing a stone at a mirror/window and the crack
widens because the energy is being released, and builds up momentum.
That is why the epicentre is not always the worst hit area. (In the
case of Sichuan, the earthquake cracked the surface in Wenchuan,
gained momentum, and had the biggest release of energy in Beichuan.
That's why Beichuan was the worst hit area)

Difference between a 7.0 to 8.0 earthquake - is 30 times more energy
released in an 8.0 earthquake.

What's important when determining how big an earthquake is: how far
the rupture is, and how far it moves.

Sichuan Earthquake

- mountains were pushed up by 4 metres after the earthquake and the
fault line (or fracture/crack) is 300km); compartively in the 2004
Tsunami, there was 20metres of motion, and the fault was 1300km long)

- compared to other earthquakes the Wenchuan earthquake has not
produced that many aftershocks,

- result of India pushing North to create the Himalayan mountain
range, and the rest of the continent moving out of the way

- Wenchuan area has three known fault strands and were studied and
well identified 20-30 years ago by the USGS. They have shared this
information with the Chinese