LAUSANNE, SWITZERLAND – A doctoral student at EPFL in Lausanne has found the key to an important aspect of earthquakes: the cause of the varying intensity, that can make the difference between a minor and major earthquake. The findings by David Kammer, published 20 February in the journal Tribology Letters, provides new material for researchers in the fields of mechanics and geosciences, who are seeking a better understanding of how earthquakes work.
Kammer has created a “digital model that explains what happens at the interface between two materials when they slide against each other; like a book on a table, rubber soles on linoleum, or – more to the point – tectonic plates,” an EPFL statement notes. “Earthquakes occur at the point where two tectonic plates meet. Between each period of sliding, forces accumulate between them up to the point where the friction resistance is released, leading to movement. This displacement of the Earth’s crust triggers a shock-wave that is transmitted to the surface of the planet.”
The researcher says he “wanted to understand the dynamics of the point at which the plates suddenly begin to slide against each other – in particular, the way it starts and is subsequently transmitted between the two solid bodies in contact. I discovered that the accumulation of energy at the breaking-point of the interface determines the acceleration of the sliding.”
Movements can be smooth and regular or can involved stopping and starting, a “stick-slip” phenomenon, and it is the latter that causes surface shock waves.
Earthquakes throughout Switzerland in the 24 hours preceding the small one in Zug: Switzerland has 500-800 a year, only 10 of which are felt (note: time is UTC and in winter Switzerland is one hour behind Universal Time)
ZURICH, SWITZERLAND – Zug was lightly shaken and stirred late Saturday 11 February at 23:45 by a 4.2 magnitude earthquake that officially qualifies as on the light end of “moderate”, with potential damage “very light”.
The earthquake had a depth of 32km. Switzerland has 500-800 earthquakes a year, about 10 of which can be felt by the population.
Four hours earlier a 2.5 magnitude earthquake hit the pre-Alps to the west of Venice, in the same area that 24 January had a 4.2 earthquake.
The most recent earthquake registered in Switzerland before this was and the most recent strong earthquake was in Sierre in 1946, according to the Swiss Federal Seismic Service.
GENEVA, SWITZERLAND – Northern Peru was hit by a 7.0 earthquake Wednesday 24 August, centred in a remote and under-populated Amazon area. The quake was felt in the capital 600 km away and in southern Brazil. The extent of the damage is not yet known.
Scientists say there is no link between this week’s earthquakes in Peru, which has a history of strong earthquakes and on a smaller scale in Colorado in the western US and Virginia in the eastern US. The latter prompted officials to evacuate the Pentagon in nearby Washington DC, schools and several tourist attractions closed in some areas and the tall, thin, Washington monument suffered cracks at the top. It is closed to visitors indefinitely while engineers study how to repair it. The Minneapolis Star & Tribune reports that only about 5 percent of East Coast residents have earthquake insurance and that about one-third of the damages, which could be $200-300 million, are insured.
Links to other sites: CS Monitor, Denver Post, Minneapolis Star & Tribune, US government earthquake hazards programme,
Zurich, Switzerland (GenevaLunch) - Natural catastrophes and manmade economic disasters cost the world $218 billion in 2010, more than three times the cost in 2009, Swiss Re, the Zurich reinsurer, said 29 March.
The loss of lives, 308,000 people, was the highest since 1976 and far higher than the 2009 figure of 15,000 lives lost, worldwide.
Earthquakes alone accounted for one-third of the financial cost.
A number of severe catastrophes claimed huge numbers of lives: “the deadliest event in 2010 was the Haiti earthquake in January, which claimed more than 222 000 lives. Nearly 56 000 people died during the summer heatwave in Russia. The summer floods in China and Pakistan also resulted in over 6 200 deaths”, according to Swiss Re, which insures insurance companies.
The cost to the insurance industry was $40b for natural catastrophes and $3b for manmade disasters.
Ten events at more than $1 billion each:
“The two biggest insured losses were caused by earthquakes – the February earthquake in Chile (USD 8 billion) and the September earthquake in Christchurch, New Zealand (USD 4.4 billion). The third costliest event was winter storm Xynthia in Western Europe, which led to insured losses of USD 2.8 billion. Three storms in the US and two storms in Australia also generated losses of over USD 1 billion.
“Property claims from the BP Deepwater Horizon explosion in the Gulf of Mexico are estimated at USD 1 billion. Given the complexity of the claims, the latter figure is still subject to substantial uncertainty. The overall insurance loss is higher, as liability losses are not included [in the report].”
The death toll from the earthquake 14 April in Qinghai province, China has risen to over 2,000, authorities say. The country will lower flags to half mast Wednesday 21 April to mourn the dead. Public entertainment will be banned.
The government has allocated 500 million yuan ($72m) in quake relief funds and more than $3.2m in aid from other countries has been offered.
Basel, Switzerland (GenevaLunch) – The CEO of Geothermal Explorers, the company that was drilling as part of a Basel geothermal energy project called Deep Heat, has been cleared of wrongdoing by a court in the city. Charges were brought against Markus Haering after the company’s drilling appeared to provoke earthquakes in Basel in 2006 and early 2007.
Basel's Deep Heat project, December 2006
Update 11:35 Basel, Switzerland (GenevaLunch) - Basel’s innovative geothermal energy project made world headlines when it was begun in 2001, but the city suffered a series of tremors in December 2006 that prompted fears the deep drilling may have triggered the earthquakes. The Deep Heat Mining project, designed to pull energy from the deep bedrock, was closed temporarily in early 2007, but Thursday 11 December canton Basel City officials announced that the project has officially closed.
The head of the Geothermal Explorers next week faces charges in Basel, and 20 Minutes reports that there is widespread surprise in the region that he is the only person who will have to answer criminal charges and that no cantonal or city officials have been charged in the affair.
Insurance claims against the project came to CHF9 million, reports swissinfo, but the project has ended, the official report published Thursday notes, because risk analyses have suggested further drilling could set off more earthquakes.
Sion, Valais, Switzerland (20 Minutes, Fre) – The news about the damaging earthquakes in the mountainous area of Italy’s Abruzzo region has prompted 20 Minutes to talk to Swiss experts about the danger zone here: Valais can be expected to have a quake on the scale of the one in Italy every 425 years, they say. 20 Minutes shows the danger zone and explains what preventive measures are taken by the canton. The last earthquake at 6.5 on the Richter scale (recalculated) was in 1855 but another between Sion and Sierre in 1946 measured 6.
