My OperaL'Aquila Earthquake - Followup
Tuesday, April 7, 2009 1:59:49 PM
At a press conference in L'Aquila today (7 April 2009) the Italian Premier Silvio Berlusconi said 207 people were confirmed dead, while 15 people were still missing, after the earthquake that hit the city of L'Aquila. Berlusconi said slightly more than 1,000 people were wounded following the quake and that 150 had been found alive. Other media now speak about 1,500 injured and some 17,000 homeless after Monday's quake.
There has been a lot of fuss about a so-called prediction of the quake. I would like to remind you what earthquake prediction is about. An earthquake prediction is a prediction that an earthquake in a specific magnitude range will occur at a specific place at a specific time. As Amphibol (in German) rightly reminds us, an earthquake was predicted to occur at Sulmora about 30 km from L’Aquila on Sunday 29 March - but it didn’t! A week later, however, on Monday 6 April an earthquake did occur, but at L’Aquila. What would have happened if the inhabitants of Sulmora had been evacuated or had fled to L’Aquila for shelter. Just think about it - and let’s face it, so far measurements of radon emissions are more or less worthless as earthquake prediction tool for all the other reasons we have heard the last couple of days.
In my post yesterday I mentioned that the quake occurred at a normal fault. When continents (like Africa and Europe) collide you would normally expect compression of the crust, but normal faulting is an expression of extension. I didn’t go into this apparent paradox, and I no longer need to as Kim Hannula at All of My Faults Are Stress Related did that extremely well in her post here.
Finally a satellite image of central Italy that shows the rugged topography in the vicinity of L’Aquila.
Lower elevations are shown in green, while higher elevations are light brown and off-white. The steepness of the mountain slopes is indicated by shading: darker shading means steeper slopes. L’Aquila is nestled in the central Apennine Mountains, which run the length of Italy like a spine. The mountains are crisscrossed by dozens of faults. Faults are not always visible at the surface, but in this part of the Apennines, many of them are revealed by steeply sloped fault scarps. A major fault system is revealed by a scarp running north-northwest from the Focino Plain nearly to L’Aquila, passing along the eastern foothills of Mt. Velino and Mt. Ocre. L’Aquila is wedged between a pair of parallel faults running toward the northwest and a long, broken fault extending toward the east.
There has been a lot of fuss about a so-called prediction of the quake. I would like to remind you what earthquake prediction is about. An earthquake prediction is a prediction that an earthquake in a specific magnitude range will occur at a specific place at a specific time. As Amphibol (in German) rightly reminds us, an earthquake was predicted to occur at Sulmora about 30 km from L’Aquila on Sunday 29 March - but it didn’t! A week later, however, on Monday 6 April an earthquake did occur, but at L’Aquila. What would have happened if the inhabitants of Sulmora had been evacuated or had fled to L’Aquila for shelter. Just think about it - and let’s face it, so far measurements of radon emissions are more or less worthless as earthquake prediction tool for all the other reasons we have heard the last couple of days.
In my post yesterday I mentioned that the quake occurred at a normal fault. When continents (like Africa and Europe) collide you would normally expect compression of the crust, but normal faulting is an expression of extension. I didn’t go into this apparent paradox, and I no longer need to as Kim Hannula at All of My Faults Are Stress Related did that extremely well in her post here.
Finally a satellite image of central Italy that shows the rugged topography in the vicinity of L’Aquila.
Lower elevations are shown in green, while higher elevations are light brown and off-white. The steepness of the mountain slopes is indicated by shading: darker shading means steeper slopes. L’Aquila is nestled in the central Apennine Mountains, which run the length of Italy like a spine. The mountains are crisscrossed by dozens of faults. Faults are not always visible at the surface, but in this part of the Apennines, many of them are revealed by steeply sloped fault scarps. A major fault system is revealed by a scarp running north-northwest from the Focino Plain nearly to L’Aquila, passing along the eastern foothills of Mt. Velino and Mt. Ocre. L’Aquila is wedged between a pair of parallel faults running toward the northwest and a long, broken fault extending toward the east.
53north # Tuesday, April 7, 2009 7:11:30 PM
The population should have been given the choice - many may have camped in an outbuilding or garage for a week. Full Moon was always going to be a time of enhanced danger. I think they should move the Champions League Final from Roma to Milano..
Ole Nielsennielsol # Tuesday, April 7, 2009 7:32:56 PM
53north # Tuesday, April 7, 2009 7:37:01 PM
Aldopiombaldo # Tuesday, April 7, 2009 8:13:33 PM
Going in outer zones you find the main actual chain (the divide is moving eastward and northeastward) and out of the main chains the valleys (that are not grabens) are longitudinal in respect of the chain.
In coastal tuscany the chain was high in miocene age. After, when the divide migrate toward more external zones, the chain collapsed, giving rise to the tectonic trenches of Tuscany
also in Central Apennines the compressional front is in the adriatic zone, east to the main chain, wich now is in the destructuration phase
the main sismicity belt is in the current main chain, and above all there is a normal fault seismicity-
The compressional sismicity is somehow lower (perhaps because the subduction in central - northern Italy is stopping?) and is placed outside of the main belt, toward the foreland
.
Ole Nielsennielsol # Wednesday, April 8, 2009 6:23:41 AM
I have a map of the main (Italian) faults, but it looks rather complicated.
I have also tried to locate the borders of the Adrian, Tyrrhenian and Ionian microplates (or blocks), but everybody seem to disagree about them!
53north # Wednesday, April 8, 2009 8:48:36 AM
=o}
Ole Nielsennielsol # Wednesday, April 8, 2009 9:43:10 AM
Why didn't I think of that
Aldopiombaldo # Sunday, April 12, 2009 7:38:36 PM
About the central apenines geology you can read a work in the last number of the "italian journal of geosciences", the former "biollettino della società geologica italiana".
Ole Nielsennielsol # Monday, April 13, 2009 7:02:17 AM
kruder396 # Sunday, May 10, 2009 9:29:01 PM
I was in L'Aquila that night and survived it. There are several things which should be said:
1. over the two months before there were lots of small quake hits which weakened the old buildings
2. the acceleration on the surface has been higher than 60%, which makes it exceptional if you consider that the new regulation on anti-sismic construction in Italy is going to prescribe that buildings has to resist 0.50%
3. it is not correct that Giuliani predicted the quake in Sulmona, actually there was some miscommunication between him and the civil defense there, but it is true that he correctly predicted the earthquake in L'Aquila, he called all his friends three hours before because according to what the instruments were recording there was something strange. He is not just measuring Radon, his techniques observe the gamma ray in the radon - he is pretty knowledgeable in this since he works at the gran sasso laboratories which are particle physics laboratories under the gran sasso mountain where there are several projects finalized to measure cosmic particle - he is not just a ciarlatan, likely he is just an engineer who was not disseinating his ideas in an accademic sound way, ie in peer-reviewed journals, he was just caring about experimenting it and avalidating agaist data etc
Just my two cents,
Alfonso
Ole Nielsennielsol # Monday, May 11, 2009 7:57:56 AM
The earthquake must have been a terrible experience for you. Hopefully further studies in how earthquakes work may one day result in less people suffering.