The earthquake is not a precursor for the big one.
"If 20-30 earthquakes of a 5.0 magnitude or so begin to occur within a month, this could be considered as a precursor for a bigger earthquake."

Professor Şener ÃœşÃ¼mezsoy commented on yesterday's 4.8 earthquake, which shook the Marmara region: "the fault line which was broken is the bridge fault line between the Çınarcık fault line, which cracked in 1999 and the Gemlik fault line which broke in 2006. The theory I have been defending for years has been proven. Now, the earthquake will follow a path from Çınarcık to the south. The 'big one' expected in Istanbul may just be hype."

Big one moves away from Istanbul

Professor Şener ÃœşÃ¼mezsoy commented on the earthquake in Çınarcık: "the earthquake is moving away from Istanbul. There needs to be 20-30 earthquakes of 5.0 magnitudes to occur within a month to call it a precursor."

The 4.8 magnitude earthquake that took place in the Marmara, on Wednesday evening caused panic amongst citizens. Two following smaller earthquakes happened last night. The specialists think that this is not a precursor for a bigger earthquake. Professor Şener ÃœşÃ¼mezsoy stated that the 4.8 earthquake has refuted the possible scenario of a bigger earthquake in Istanbul. ÃœşÃ¼mezsoy stated: "The fault line, causing the recent earthquake is the bridge fault line between the Çınarcık fault line, which broke in 1999 and the Gemlik fault line, which broke in 2006. The western part of the broken fault line has cracked up to Esenköy. The Bozburun fault line continues to the southern part of İmralı. From now on, the fault line will take on a path directed south; which means not towards Istanbul."

SABAH 14.3.08

http://english.sabah.com.tr/5739DE86F73E4B1DBDBAC252DF71442E.html

Usually, I can feel the P-waves very intensely, I did feel this last one too. With earthquakes happening in remote places, it gives you a few seconds to escape outside the building but then earthquakes happening hundreds of kilometers away are often not very destructive where you live. The only time you should be really concerned is when the perimeter is closer than 50 or so kilometers in the case of major earthquakes or when you are directly on the fault line.

At the time of the big earthquake on September 17,1999, I thought the building I was in would just tumble down as a whole. I remember trying to hold the cement beam on the ceiling instinctively as if trying to prevent it from falling down on us. I did not have the time to calculate in panic, that each cubic meter of it weighed several tons, and that it would crush us instantly did it ever fall on us.

I could not get rid of the fear and the psychology of the earthquake for years. Even today, when I experience a minor earthquake my mind takes me back to that catastrophy that claimed the lives of 50 thousand, maiming 100 thousand and leaving 600 thousand people homeless.

The earthquake lasted for 45 seconds but those forty five seconds felt like maybe ten years. It was caused by the breaking of a fault line stretching hundreds of kilometers.
The original perimeter was 150 kilometers from where I lived but it was felt in a radius of at least 4 or 5 thousand kilometers at various strengths. The magnitude was 7.5 on the Richter scale, some sources measured it at 7.8.

You had a brush with death, be glad you are alive!

Yet all of the talk above does not mean anything, none is supported by evidence, I mean scientific evidence. There are other academicians telling otherwise. What I mean is, if you have neither evidence nor facts, what you tell is pure speculation, nothing more.

Telling people not to be afraid and that everything will be all right will do no good but much harm. After the '99 quake, the slogan told by academicians was "Depremle yaşamaya alışmalıyız - We should get used to living with the earthquake" meaning of course, "Turkey is a place with earthquakes happening all the time, so we should take precautions and so."

Nine years have passed since, and we did get used to living with the earthquake all right! Sadly in a Turkish way of course, just by forgetting all about it. Nine years have passed and what effective measures have been taken? None, save a few 'see-we-serve-you' show-drills and 'quake containers' scattered over the city, locked securely, keys of which are god knows where. I secretly wonder what awaits inside those pretty orange-painted containers (which are now rusting slowly). A trained SAR team and their dogs to locate and rescue the injured quicly? Maybe a medical team complete with an operating theatre and ICU? Food (already rotten) or medical supplies (will be administered by whom?) to aid the survivors? A magic device that prevents the buildings from collapsing, no? And if there was something useful inside, who will distribute them and prevent looting? My guess is just body bags.

After 1999, Tubitak (The Scientific and Technological Research Council of Turkey) -one of the few reputable organisations of Turkey- published a report about the effects of a hypothetical 7.5 magnitude earthquake in Istanbul. Estimates were more than 150,000 dead and ten times or more injured, thousands of buildings collapsed or uninhabitable.

If one remembers the fact that of the one and a half million buildings in Istanbul, over seventy percent were illegally built without permits and not adhering to any kind of building code or whatsoever, these estimates sound somewhat optimistic. Of course, the report fell on deaf ears, just like the earthquake seminars held in the city of Izmit, named "Is Izmit ready for an earthquake?", mere months before '99 Izmit quake. Irony.

In the month of Ramadan, light fixtures called 'Mahya' are customarily put up between the minarets of mosques, spelling some religious words and hadiths at night. After the quake, in the Ramadan of '99, all 'Mahya's in Istanbul were banned. The papers reported the reason was "They would interfere with the natural resonance of the minarets and may cause collapse in the event of an earthquake." The next year's Ramadan was too without 'Mahya's. But 2001 came and they silently came back again. Since then they are up every year. Why, I ask. Did they not pose any danger in the first place? Was this such an unimportant issue and abondoned? Or are we now sure that no earthquake will happen here? Nobody knows and nobody cares for such details. Details like fixing heavy furniture at public buildings, especially schools. Details which will decide someone will live or not. Irony.

"İstanbul'u dinliyorum, gözlerim kapalı." I sometimes do that, as the poet says. I hear screams of the dying, crushed under tons of concrete. I hear the pleads of a woman desperately looking for somebody, anybody who will help her loved ones trapped in the rubble. I hear doctors shouting amidst total chaos in the emergency unit of a hospital. I hear people on the bloody hospital corridors, fighting to be treated first. I hear men fighting over a piece of food. I hear firefighters unable to reach a burning building because the streets are blocked with collapsed buildings. I smell a hundred thousand rotting corpses, as no one knows who will deal with them and how. Then I hear the military stepping in and declaring martial law. I open my eyes.

Does anybody think like me? I don't know, but people around me don't. Am I being too pessimistic? I hope so. Is this the most important issue in Istanbul right now? At least, is this an issue which needs to be dealed quickly and seriously? What can be done? Can anything be done? I wish I knew the answers.

To this day, effectively nothing was done to minimize life loss, there is no serious 'afterwards plan', no nothing. Yes, we're merrily living with the quake, I think we got used to it at last. Not by planning and working, but with laxity, ignorance and forgetting. Welcome to the land of irony. Welcome to Turkey.

Thank you for reading and I apologize for any grammatical errors.

Lazy42:I understand what you are saying, but are not geologists able to estimate the probabilities of a certain level of earthquake within a period of time? For ex. could one say that there is a 60% probability that Istanbul would suffer a 6.0 or more magnitude earthquake within the next 20 years? This may not seem helpful, but I think these kinds of estimates are accepted by geologists. Do you think so?
They say the same thing about the San Andreas Fault Line in S. California.

A strong earthquake shook southern Mexico recently, causing panic and minor damage to buildings and prompting an oil refinery to shut down as a precaution. There were no reports of major damage or injuries.

The magnitude-6.4 quake was felt across hundreds of miles, gently swaying buildings in Mexico City and rocking parts of Mexico’s Gulf coast.

In Tuxtla Gutierrez, the capital of Chiapas state, which Roswitha knows very well from her travels many people fled into the streets and then lingered outside their homes, fearing aftershocks.

Mexico’s state-run oil company Petroleos Mexicanos shut down its Salina Cruz refinery on the southern coast as a precaution immediately after the quake struck.

The U.S. Geological Survey said the quake was centered 70 miles southwest of Tuxtla Gutierrez, near the border between Oaxaca and Chiapas states.

More from msnbc.com

Roswitha, you are totally correct about estimating a quake in a period of time. Northern Anatolian fault zone is a 'strike-slip' type fault, it slips sideways. San Andreas is nearly identical. The good news is, strike-slip type faults are predictable. Using satellite laser or radar inferometry it's possible to determine energy build-up stress zones, where unreleased energy may be measured and an estimate can be made about the time of breaking.
The bad news is, afaik this works on the land only. Alas, the NAF dips into the sea at west of Yalova, and goes more than a hundred miles until resurfacing. In the past there was much debate over the undersea fault being continious or broken into two pieces. A Turkish geology ship and later a French ship did some measurements and experiments that time but there was no clear result or prediction. Or maybe the results were so horrible that they were hidden?
Usumezsoy is an academician, yet there are others telling otherwise. I'm not saying he is wrong, he may be right. But since '99, after any significant earthquake, each TV station here grabs a geologists, puts him/her on air and broadcasts their speculations. The geologists themselves are accusing each other on TV, papers etc. and quarreling about who is right, although none have any proof backing up his/her hypothesis. The whole thing is like a circus.
I meant to say that none of those hype and babbling are gonna help people, and telling that 'the big quake' just won't happen is wishful thinking.

Thank you for your well presented reply!