Earthquake

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Earthquake

The Norwegian Natural Perils Pools has only registered a few claims reported as caused by earthquake.  Almost every one has been repudiated, as no earthquake has had the strength which should cause damage. 

Earthquakes are tremors under the surface of the earth which are caused by sudden release of stress in the earth crust. The point where the release takes place is named hypocenter, while the point on the surface directly above the hypocenter is named the epicenter.

During an earthquake elastic vibrations take place in the earth crust.  The vibrations become weaker the further away you are from the center. Large earthquakes may cause extensive damages.  During earthquakes at the seabed, large tsunamis may occur.  Earthquakes take place where there are movements in the earth crust, and in particular at the boundaries between earth crust plates.

Link to the Norwegian National Seismic Network

There is more than one table for recording earthquakes:

1.


 Richter Magnitude Scale is based on instrument measuring (seismograph). The energy released in a quake is measured.  Richter’s scale is logarithmic – e.g. a quake of magnitude 6 on Richter’s scale releases approximately  32 times more energy than an earthquake of a magnitude of 5 on the same scale.
2.

Mercalli’s Magnitude Scale is a scale bases on the consequences from 1 to 12. It is based on observations in the country side of the damages done and then next  the extent of the damages is put on to the describing scale.


A chart showing Mercalli’s scale can be found in enclosure 18.

The largest earthquake which has been recorded in Norway the last 100 years, was a quake in the Oslo area in 1904, which was recorded at Richter’s scale at 6 and transferred to magnitude 7 at Mercalli’s scale (“light” damages to buildings, personal chattels and glass together with wrecked chimneys).

Collection of facts in connection with reported damages shows that the main reason quite often is not
the earthquake, but has its natural explanation in:

Subsidence cracks
Shrinkage cracks
Expansions
Heating of cold chimneys
“Broken” seal in windows/mist/leakage
Ground pressure
Cracks in laps
Weak fastening devices
Stress in floor, walls and ceiling
Weak strut-brace
Shrinkage of wall plates
Old roof covering
Frost and ice
Faulty foundation
Material dividers

The list is not complete.

Be aware of the fact that the collection of facts in connection with reported damages caused by earthquakes, means very hard and demanding work for the surveyor, so in cases like these, only surveyors being in particular competent in this line of work shall be used.

All ordering of surveys on damages caused by earthquake shall be done through a main coordinator in the area where the damage has occurred.

If the case is being appealed, the reply from the company shall be sent The Pool for consideration before a final decision is taken.

Appeal cases: 

291/90  Residential house – over time/cracks  no natural damage.
   6/95  Residential house – poor repair of old damage no natural damage
  30/95 Holiday home – no causal connection  no natural damage
  42/95 Pump in well – no causal connection  no natural damage


See also the chapter about main cause