Italy's new seismic hazard map rejected

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Ninis, Dee

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May 20, 2023, 6:21:23 AM5/20/23
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Hi all,

I thought this might be of interest:

Regarding the new seismic hazard map for Italy, "the National Institute of Geophysics and Vulcanology (INGV) has completed the internal evaluation of the map, and that the outcome was negative. This means the new map has effectively been rejected... because it relies primarily on historical data and neglects geological, geodetic and rheological information” 😬  

More here (though nothing about magnitude conversions, unfort.):

Cheers,

Dee

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Dee Ninis

Earthquake Geologist - Seismology Research Centre

141 Palmer Street, Richmond VIC 3121, Australia

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Research Affiliate - School of Earth, Atmosphere & Environment

Monash University


I acknowledge and respect the Traditional Indigenous Custodians of Country throughout Australia, and Elders past and present. I recognise their cultures and continuing connection to land, waters and community. 






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Dee Ninis

Earthquake Geologist - Seismology Research Centre

141 Palmer Street, Richmond VIC 3121, Australia

T +61 3 8420 8998 F +61 3 8420 8900

Find us on our Website, Facebook, Twitter and YouTube



Research Affiliate - School of Earth, Atmosphere & Environment

Monash University


I acknowledge and respect the Traditional Indigenous Custodians of Country throughout Australia, and Elders past and present. I recognise their cultures and continuing connection to land, waters and community. 

Kevin McCue

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May 21, 2023, 4:04:37 AM5/21/23
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Thanks Dee
Interesting but what is the lesson for Australia do you think?
What geological, geodetic or rheological data do we need here to improve earthquake hazard mapping?

I, for one, would strongly advise anyone doing earthquake hazard analyses in Australia to consider historical earthquake information, there is a wealth of it available though not comparable with the Italian database. Such studies should have guided the recent hazard assessment for the Australian Building Code. Had more complete studies of historical earthquakes been done in Christchurch NZ, authorities might have come up with more stringent design earthquakes there, take the following example:

Riverine Herald (Echuca, Vic. : Moama, NSW : 1869 - 1954; 1998 - 2002), Wednesday 14 September 1870, page 2
The severest earthquake that has occurred here since the 5th June, 1869, was experienced at Christchurch, (says the Lyttlton Times) on the 31st August, about twenty-three minutes past six o'clock, according to the clock at the Government buildings. Opinions differ as to the direction of the earth wave, but the most general impression is that it was from east to west. There were ap -parently two distinct shocks, with the interval of several seconds between them, nearly three quarters of a minute elapsing from the first indication of the earthquake until the tarmination of the second shock, which was the most violent. In Christchurch, a chimney was thrown down in Chester-street, but no further damage has been done so far as we have been able to ascertain. The shock was severely felt in the neighborhood of Papanui, and likewise in Kaiapoi and Tamaka. Considerable damage has been sustained in Lyttleton, a telegram from there informing us that two severe shocks of earthquake were felt at 6.22 p.m., lasting for thirty seconds; that several chimneys were thrown down, and that people rushed from their houses in the greatest fear. A genteman living in Christchurch writes as follows — As near as I could mark it, the shock of earth-quake this evening commenced at twenty-three minutes past six o'clock. It came from the S.S.E.
An observer standing out of doors at the time saw a wall and a gate before him rise and fall apparently several feet. A four-wheeled carriage, standing in the direction given above, was pushed some feet forward towards the north. Within the house the bells were set a ringing, and a chandelier suspended from the roof continued to vibrate for about twenty minutes. There was another, but very slight shock at about twenty-fire minutes to seven o'clock.

Neither this 1870 earthquake, nor that referred to in 1869, are in Gaye Downes Atlas of Isoseismal Maps of NZ Earthquakes but the information has been available for more than 150 years, had historians looked
Kevin McCue

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Brendan Duffy

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May 21, 2023, 7:05:13 AM5/21/23
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Hi Kevin,

I think you'll find all of these were discussed in detail in an early 90s report by Jarg Pettinga and others. Jarg and Dave Bell routinely objected to the development of liquefiable land and their objections were just as routinely ignored, in part because of low geodetic strain rates and a mischaracterisation  of the Alpine fault as the main hazard,  instead of smaller local quakes. Representations on building codes were equally futile. So yes, it's a lesson but not because local scientists forgot or didn't think to both document and communicate the hazard.

Regards

Brendan 
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Subject: [EXT] Re: [aees] Italy's new seismic hazard map rejected
 
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da...@earthquake.net.au

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May 21, 2023, 10:19:01 PM5/21/23
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Hi Brendan

 

While on the code committee trying to make a joint A/NZ code long ago, I can the remember the gist, but not the detail.  There was a strong push to have no soil type E.  “All those should have a special site specific study” was the argument.  But there was a strongly put argument that type E was essential.  I remember the plea “But what will we do with Christchurch?”

 

Regards

David 

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