tiny earthquake

Haven't felt one in a while.... but just felt a tiny rumble of an earthquake. It was rather cute actually. Maybe it will pop up on JMA later....

ahhh here it is. Apparently a M5.2, with a JMA maximum intensity of 3.

5.8M wake-up call...

Felt another earthquake this morning.　It has been a while since i felt one. It was quite nice and gentle, but it did wake me up as it went on for nearly a minute.

5.8M (JMA scale) around 7am this morning.

Your Mission, should you choose to accept it...

I've been invited, by my Professor, to join a JGS (Japanese Geological Society) collaborative mission to China, following the SiChuan Earthquake in May.

The dates of travel have now been set, although we are still unsure of where precisely we will be allowed to visit (due to safety issues and other less official factors). The visa applications are on their way and details of our journey to ChengDu are being finalised via a volley of emails. I am starting to feel like I should be more important than I actually am. Having glimpsed the list of the Geotechnical Team Members, I am the only female and possibly the least qualified person on the entire team.

I am starting to feel very small.

Sichuan Earthquake Mw7.9

A huge earthquake has hit the SiChuan [四川] Province of China. Reported to have a moment magnitude* of 7.9 (USGS) hit at 2:28pm. In the first few hours of the news being reported they only stated 5 people having died, 4 being children killed when part of a school collapsed and the main damage being burst water mains which were flooding the streets. Hitting in the middle of the day has its pros and cons: on the bright side nearly everyone is awake and has been a wake for a while so should be able (if capable, which may not be the case in such a large earthquake) to react and make some attempt in sheltering and saving themselves, they are not at home and they are not travelling and so would/could/should be a little safer. On the down side the population will be concentrated in the city and if one of those buildings collapses you'll get more casualties in one go. Half a day later, there are reports of 900 odd students trapped in a collapsed university# building and this morning there are photos of lines of bodies which were found buried in the rubble. The first 10 mins of a quake are most likely going to decide your fate, then after that you have to worry about fires...

Hopefully, it wont detract too much attention from Burma, which is still facing a monstrous disaster with the government refusing to allow aid and aid workers in. Which is very curious. Even Iran willingly let in the enemy that is the US to help with the 6.6Mw Bam earthquake 2003, which claimed 50 000 lives (according to Iranian sources, and 31000 according to the USGS).

*Moment magnitude [Mw] is a different magnitude scale from the more commonly recognised Richter scale. There are many magnitude scales for judging earthquakes; Richter is a local magnitude scale and is not really applicable to comparing earthquakes from different regions; Surface wave magnitude [Ms] are based on the amplitude of the surface (Rayleigh) waves which can still be measured a greater distances from the epicentre of a earthquake - more commonly used to describe shallow earthquakes; Body wave magnitude [mb] is used for smaller intra-plate earthquakes with a deep focus, as very few surface waves are generated, and instrumentation would be close enough to pick up the body waves before they are attenuated. All apart from moment magnitude suffer from 'saturation' where the scales become insensitive to further increases in earthquake energy. To put this into perspective the bomb that hit Hiroshima was just over a magnitude 6Mw, and the earthquake that hit Chile in 1960 was a 9Mw. - all this information can be found in Kramer (1996) Geotechnical Earthquake Engineering.

#actually, I would like to correct this, it was a middle school where 900-1000 children/teenagers and teachers are trapped in Juyuan [枸橼], Dujiangyan [都江堰] when one of three school buildings collapsed from 7 stories to about 2m in height. The two other buildings only partially collapsed. There was also a separate case of a different middle school having collapsed with around 100 people inside. article by Xinhua here.

more earthquakes

Two more earthquakes this morning, 4.5 and 5.7 (Japanese scale), not as big as yesterdays...but brings the total up to 7.

my strongest earthquake yet

So far the tally on earthquakes that I have felt since coming to Japan, lies at a measly 5. Two of them were felt last night, the first happened around 130am and was just a gentle rocking of our apartment, whilst the second was the longest and largest that I had felt to date. It lasted about 10-15secs to my reckoning and shook the apartment pretty well, mainly by rattling the doors. At one point I was a little worried that it would get stronger and I did start contemplating getting out of bed to hide under the table or something, but it wasn't necessary.

Anyway, it turns out that these two tremors were caused by quite large earthquakes off Ibaraki prefecture [茨城県沖], JMA magnitudes 6.3 and 6.7 respectively.
The above diagram of seismic intensity (different from magnitude) - the level of shaking that different places felt/experienced is taken from the JMA website for the 6.7 magnitude quake, direct link here.

...Earthquake Early Warning System...

The JMA (Japanese Meteorological Agency) [気象庁 - きしょうちょう] - I was actually looking up the weather forecast for the next few days, and got heavily distracted... (but in an educational way...) - and saw that they have something up about their 'Early Warning' System.... I was just having a peek at how much warning they were able to give, just in case they'd managed to somehow miraculously come up with a way to predict earthquakes before they happen - I live in optimism...possibly a slightly deluded optimism...ANYWAY...I was a little disappointed (but not particularly surprised) that the warning of a strong tremor is zero seconds, or to the order of 10's of seconds if you're lucky...

my first earthquake

Yeah...I've only been here 10 months, with lots of earthquakes going on that seem to bypass me...and FINALLY on Thursday.

It being 4am...it was subconsciously incoperated into my dream...when I did finally open my eyes, I awoke to Greg sitting up looking at me, saying: 'wayway...earthquake'... Had my vocal chords been in gear, I would have answered, but they were in sleep mode, so I dreamily experienced the room rocking backwards and forwards. my immediate thought was; 'it's got to be quite a big one. and quite close to Tokyo...hmmm....nice.'

Then it stopped.

'How big do you think it was?!' say's Greg, who had obviously been up for a while before the earthquake...

'Oh...I don't know!' - thinking it's very early in the morning to be asking such a question... I'll google it later.

'Go on guess! just for fun!'

...oh god.
'...arf... 5...it's got to be close...didn't feel all the other ones...we're too low down....' I mutter...if I answer him, then maybe I can go back to sleep...