For those who are living in Japan and have few experience about earthquakes: I suppose most of you are living in the Tokyo region. This place is safe for now. Yesterday's M9 earthquake was a serious disaster and affected a wide region of northeast Japan. I believe you could also feel the aftershocks yesterday all night. Most of those aftershocks were harmless. Even if they do, it's likely that they will affect the same region, not Tokyo.
Please, however, do not simply assume that the safety will last indefinitely. If you have not heard about the following before, I think it is now time to pay some attention. It is the government's policy that Tokyo is expecting at least one severe earthquake disaster in the near future. Technically, the accepted prediction is that there is a very high chance (~70%, depending on region) that the Tokyo region will suffer from a JMA intensity 6+ earthquake (which will cause building damage) somewhere in the next 30 years. I know it seems difficult to understand these numbers. For some people, 30 years look a long time and irrelevant to your current life. Unfortunately, under the current level of science, it is difficult to give a scientific prediction with better resolution (i.e. shorter period of time). Anyway, in simple terms, earthquake WILL come, sooner or later.
A minor point to add about earthquake prediction is that, actually Miyagi Prefecture (the center of disaster for yesterday's M9 event) is categorised as a highest risk region. It is not surprising that a disaster will hit, although it's still out of many experts' expectation that the magnitude is this large. I am sure that you must have also heard from the news that this is the largest earthquake we have ever had in the history of Japan (more precisely, in the instrumental history of Japan; no one knows that happened 10000 years before). Yes, we are witnessing the history.
Another thing I would like to remind (or advise, in case you did not know it before) you is that, for a M9 earthquake of this kind, it is not surprising that it will trigger some moderate earthquakes in the nearby region. Some aftershock you felt today and yesterday may not be technically aftershocks but triggered earthquakes. Differentiating them precisely is left as an exercise for scientists. What really related to your personal life is that, these triggered earthquakes could occur somewhat far away from the mainshock. Today's (12th March) early morning, there was a M6.2 earthquake in Niigata Prefecture inland and caused some damage. This level of earthquake magnitude is comparable to the previous Niigata earthquake in 2007 that damaged a nuclear power plant, and another previous one in 2004. That means, even if there was no M9 earthquake yesterday, the Niigata earthquake in this morning by itself is a major disaster already. It was fatal, and likely be fatal again if similar things happen again.
We all know that it is not an aftershock. Whether it is a coincidence or a triggered event is unknown for now and probably will remain unknown in the near future, but let us assume the worst. From previous experience, after an M9 class earthquake, there will likely be a continuous swarm of moderate earthquakes, either aftershocks or triggered earthquakes, in the next one month. Triggered earthquakes can even come somehow later (say, a year later) and in a relatively far place from the mainshock (say, Niigata from Miyagi, or even Kanto region).
If you have not ever imagained that an earthquake will hit you before, think about it now. Think what you will do after an earthquake has hit you place. How do you contact with your family members or close friends in case telecommunications are not functioning? Where is your nearest emergency gathering site? If you are living or working in a place close to water (say, with a beautiful sea-view), how is the tsunami risk? The tsunami risk for Tokyo city is not expected to be high, so there is no official predicted flooding depth for tsunami scenarios. For some regions in Japan, there are official predictions. All information is open to the public. You can search for "tsunami shinsuiyosoku" (in Japanese, in English it means tsunami flooding prediction) to check if there is any official tsunami prediction for your area.
Natural disasters may or may not be predicted, but certainly cannot be prevented. Earthquake will come, sooner or later. A prepared mind will keep you claim during emergency, may save your life, and very likely make your life easier in the post-shock time. Be prepared!
轉載小弟一位舊同學的fb，此君在日本從事地震研究多年
