There has been a lot of activity over the last week or so (while I have been on holiday with the kids). It is really good to see stations picking up smaller events (M6.4), I have noticed that the background noise on my station (KEYW) is significantly less as summer approaches than it was over the winter. (Are seismometers just fancy weather stations after all ?) well done Pete for being first to spot these latest events.

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The Helicorder trace from PAUL shows the two M 6.4 earthquakes today , the first at 01:57 UT in the Batan Islands region of the Phillipines and the second at 14:31 UT in the Macquarie Lslands.

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There was a M 6.2 earthquake in Iceland at 15:46 UT today.

 The epicentre was at Selfoss 50km from the capital Reykjavik, being a shallow event (10Km) there was a lot of shaking and there are reports of serious damage to buildings and the road between Selfoss and Reykajavik is closed, thankfully at this time there are no reports of casualties. The bbc news website carries the latest reports and video of the earthquake. Update; 20 people treated for minor injuries.

The trace and travel time curves from PAUL were retrieved from the IRIS site using the "stations " programme, PAUL is continually uploading data via "upload". (apart form the occasional glitch!)

{{file:662}}      {{file:663}}

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{{file:644}} Earthquakes on mid-ocean spreading ridges are very common, however they are usually smaller than M6.0 so this event (Mw=6.4) is quite unusual

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What is the point of seismology if it cannot predict or prevent earthquakes? As the casualty figures from China approach 50,000 this is a question that you might find yourself being askled or asking yourself. It is a very important question that every seismologist has to answer at some point in their career. I usually end up talking about the things that seismology has been able to do. We have been very succesful at probabalistic analysis of earthquakes. For any location on the planet it is possible to calculate fairly accurately what the probability that a certain threshold of ground shaking will be exceeded within a 50 year period. This is not useful for evacuating populations before a big event but it is used extensively to ensure that building codes in earthquake prone zones are sufficient to withstand the likely effects. Unfortunately many earthquakes happen in areas where building codes are not adhered to or have many buildings thta are too old to be covered by these recent advances in understanding. In many cases effective mitigation of the effects of earthquake is a political and economic problem rather than a technical scientific one. Scientists need to ensure that the results of their research is communicated effectively to those in power in the field of seismology as much as in other fields (eg climate change)

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As the events of the day unfolded and the casualty list grew from an initial count of zero 9at 09:30 to over 8000 by 5pm I was reminded of the most penetrating question ever asked of a physics teacher "Sir, when there is a big earthquake are you happy or sad" (asked by a young student of Stewart Bullen's many years ago). This morning when I first saw the email about this event I thought "Oh No" because big earthquakes in China have a record of causing massive casualties. I was initially reassured by the BBC, but as the true extent of this tragedy unfolded I became dismayed and saddened by the tragedy of the event.

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This is the trace from WINWM just south of Birmingham. We also got a count of almost 30,000.

It's good to see a trace like this, but it's going to be a human tragedy.

http://www.scispace.net/daveb/files/-1/632/China+earthquake.JPG

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A large earthquake (reported by USGS as Mw=7.8 or 7.9 Ms=8.0 or Mb=7.1 reported magnitude has been upgraded from 7.8 to 7.9) hit China this morning. Earthquakes in China are potentially devastating, initial reports on the BBC suggested that this was a sparsley populated area and many buildings in cities nearby were evacuated no casualties had been reported by(09:30). UPDATE by 5pm there are reports of 8000 fatalaties (including an entire school). This number of casualties is only likely to increase as rescuers reach the affected areas. The event was spotted by George Marshall at Robert Smyth school on his seismometer before he checked the news. {{file:631}} The signal at KEYW shows P(06:39) PP(06:42) S(06:49) SS(06:53) Surface Waves(7am onwards). The Surface waves registered near the maximum possible on the SEP system (30,000 counts) giving a an estimate of surface wave magnitude >8.5. If you did not record this event then your station is not working. more info on this event at http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/us2008ryan.php

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21:51:31 9th May M 6.7 Earthquake Guam

{{file:629}}      {{file:630}}

 

Pete hill

Paulet

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{{file:627}} A series of events offshore Japan, M6.2 at 16:02, M5.9 at 16:16 and M6.8 at 16:45. The signal at KEYW looks very confusing with the surface waves from the first event overlapping with the body waves from the last one.

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