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Thread: Christchurch - Was this the strongest earthquake shaking recorded anywhere ever?

  1. #1
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    Default Christchurch - Was this the strongest earthquake shaking recorded anywhere ever?

    There's an interesting table in the Wikipedia here.

    The shaking an earthquake causes is more closely related to the peak ground acceleration (PGA) than to the Richter magnitude. (Duncan74 has already talked about acceleration here.)

    According to the Wikipedia table, the highest PGA ever recorded in an earthquake was the recent one in Christchurch.

    PGA....... Richter.. Depth...... Fatalities... Earthquake
    2.2g 6.3 5 km 166* 2011 Christchurch
    1.7g 6.7 19 km 57 1994 California
    1.26g 7.1 10 km 0 2010 Canterbury
    1.01g 6.6 10 km 11 2007 Chu-etsu
    0.8g 6.8 16 km 6,434 1995 Kobe
    0.78g 8.8 35 km 521 2010 Chile
    0.51g 6.4 ? 612 2005 Zarand
    0.5 g 9.0 32 km ? 2011 Sendai
    0.5g 7.0 13 km 92,000 2010 Haiti
    0.24g 6.4 ? 628 2004 Morocco
    0.18g 9.2 23 km 143 1964 Alaska
    0.125g 7.7 44 km 27 1978 Miyagi

    (I see that most of the measurements are from the year 2000 onwards. I expect this is a result of more measurements being taken in recent years rather than the number of big earthquakes increasing worldwide.)

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    I am not really a big fan of Wikipedia but that article is quite good.

    It is correct that the acceleration is generally a more appropriate method of measure than others but it too as it's limits. A quote out of that article:
    "In an earthquake, damage to buildings and infrastructure is related more closely to ground motion, rather than the magnitude of the earthquake. For moderate earthquakes, PGA is the best determinate of damage; in severe earthquakes, damage is more often correlated with peak ground velocity."

    Undeniable the Chch earthquake is not a moderate one but a severe one! Thus the velocity becomes more relevant as the (peak) acceleration might not have lasted long enough to be the only true representative.

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    Default Factors combined to worsen Christchurch quake

    http://www.odt.co.nz/news/national/1...tchurch-quake:

    According to GNS Science, four factors caused the intense shaking from the Port Hills fault earthquake; the energy released in the fault's rupture, the direction it was released, the "trampoline effect" between layers of sediment and the proximity of the fault to the city.

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    Thanks Ralf. Do you know if there's any ground velocity data for the Christchurch quake?

    (The Wiki table has been updated and the earthquake that caused the recent terrible tsunami in Japan is reported to have had a PGA of 2.99.)

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    Quote Originally Posted by ENZ View Post
    Thanks Ralf. Do you know if there's any ground velocity data for the Christchurch quake?
    No I don't know right now. Still waiting for that to be published.

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    Apologies if this is a repost but I found the photos contained in this link as being particularly enlightening to those of us fortunate enough to have never experienced the destruction of the earthquake in NZ

    https://picasaweb.google.com/RossBec...80418760038434

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    It's albums like this that make me wonder at the the fact that *more* people didn't die. Seriously. I know it was bad, just from my own experience, but given the time of day and the number of severely damaged buildings... it could still have been worse.

  8. #8
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    Regarding PGA, how accurate were these figures for the early earthquakes? I mean the one in Alaska in 1964, I didn't know they had equipment to detect PGA for that earthquake.

    I was told that the Christchurch quakes was a 1st to record PGA to such detail and accuracy never done before.

  9. #9
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    We were in an earthquake on 14. oct 1968 in Perth, aparently it was centred in a place called Meckering, we were told at the time that it was 7.2, but they seem to be publishing it at 6.9 now. It was rough a 4ft drop apeared in a road, our house which was double brick had cracks.

    Gran

  10. #10
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    Quote Originally Posted by ENZ View Post
    There's an interesting table in the Wikipedia here.

    The shaking an earthquake causes is more closely related to the peak ground acceleration (PGA) than to the Richter magnitude. (Duncan74 has already talked about acceleration here.)

    According to the Wikipedia table, the highest PGA ever recorded in an earthquake was the recent one in Christchurch.

    PGA....... Richter.. Depth...... Fatalities... Earthquake
    2.2g 6.3 5 km 166* 2011 Christchurch
    1.7g 6.7 19 km 57 1994 California
    1.26g 7.1 10 km 0 2010 Canterbury
    1.01g 6.6 10 km 11 2007 Chu-etsu
    0.8g 6.8 16 km 6,434 1995 Kobe
    0.78g 8.8 35 km 521 2010 Chile
    0.51g 6.4 ? 612 2005 Zarand
    0.5 g 9.0 32 km ? 2011 Sendai
    0.5g 7.0 13 km 92,000 2010 Haiti
    0.24g 6.4 ? 628 2004 Morocco
    0.18g 9.2 23 km 143 1964 Alaska
    0.125g 7.7 44 km 27 1978 Miyagi

    (I see that most of the measurements are from the year 2000 onwards. I expect this is a result of more measurements being taken in recent years rather than the number of big earthquakes increasing worldwide.)
    The most recent NZ Geographic shows a much higher PGA (2.7!) for the Sendai quake. All of the other metrics match their table.

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