This diary entry gives an expert geophysicist's personal view into the events of the March 11 earthquake from the beginnings.

• 12:57 13 March 2011 by Robert Geller, University of Tokyo, Japan
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When the earthquake struck at about 3:00 pm on Friday March 11 (Japan Standard Time), I was in my office on the 7th floor of the School of Science Building of the University of Tokyo, typing away on my notebook PC. Moderate-sized quakes are not uncommon in Tokyo, so I kept on typing for a while, ignoring the shaking.

However, as a seismologist, I immediately recognised that the amplitude of the seismic waves was large, but that the shaking was relatively long-period, with an almost complete absence of the sharp jolts that characterize nearby quakes. (This is because the earth gradually absorbs seismic waves as they travel, and shorter period waves are absorbed over a smaller distance range.) Because I could quickly identify this as a large, relatively distant quake, I didn't worry too much. Even so, as the shaking continued, I ducked under my desk for a while to guard against papers and books falling on my head from the cabinets behind me (in the event almost nothing fell out).

When the shaking stopped after a couple of minutes I got back to work, and when my students looked in to see if I was OK I told them, perhaps a bit too sharply, to get back to work. After a few minutes the safety office decided we should evacuate the building, and I complied (although I – correctly as it turned out -- didn't think this was necessary). Everyone climbed down the stairs, and after a half hour or so milling around we went back in and got back to work. We had to use the stairs, since the elevators were turned off as a safety measure.

Since the trains were stopped as a safety precaution, I walked home (55 min) rather than taking the subway (30 min, 7 of which on the train, the rest walking to and from the stations), which wasn't a problem as the weather was fair. When I got home I found no damage, but the gas had been automatically cut off by a quake detector. Pushing a button on the gas meter restored service.

The phone network was overwhelmed, but eventually (8 hrs after the quake) I got through to my wife and her mother and sister, who were on vacation at a hot spring resort in Northern Japan, and confirmed their safety. I was a bit luckier than most Tokyoites-many were stranded overnight at their workplaces, but even for them there was no danger, only a bit of bother. And now, 32 hrs after the quake as I write this, things in Tokyo are steadily getting back to normal.

Unfortunately, however, the situation is drastically worse in the hardest-hit areas. The TV news has been 100 per cent focused on the quake and the resulting damage. Truly horrific scenes of whole towns that have been almost completely destroyed by the quake and tsunami are replayed regularly. And many survivors, having lost all of their possessions, are taking refuge in temporary facilities under spartan conditions, without electric power or heat in many cases, although they do all seem to have food, water, and blankets.

A nuclear power plant in Fukushima has suffered severe damage and radioactivity has leaked out, with an evacuation of local residents within 20km of the plant having been ordered. The full severity of the damage to the power plant is not yet clear from news reports.

In summary, many of the earthquake countermeasures taken by Japan have been successful, at least in part, but no conceivable economically realistic countermeasures could have precluded substantial damage from a magnitude 9.1 quake and the resulting tsunami. The immediate focus must now shift to rescue and rebuilding measures. Further down the road, lessons from the quake and its aftermath must be reflected in public policy. Not the least of these is that when we're thinking about future earthquakes we should, as noted by Hiroo Kanamori of Caltech, "expect the unexpected."