Stories tagged fault

Nov
11
2011

On November 10, 2011, at 17:25 UTC (or 11:25am Central Standard Time), a shallow quake occured in Greece about 11.8 miles NE of the town of Patras. According to the European-Mediterranean Seismological Centre, this earthquake had a magnitude of 5.1 (later downgraded to a 4.6) and was a relatively shallow quake at 5 km (approximately 3.1 miles) below the Earth's surface.

This region is characterized by a high level of seismicity, and small tremors are continually recorded along the coast of Patras. Another interesting aspect of Patras is that in antiquity, there was an ancient oracle, over a sacred spring, dedicated to the goddess Demeter. Professor Iain Stewart from the University of Plymouth has been studying a supposed link between ancient. sacred places in Greece and Turkey and seismic fault lines. Many ancient temples and cities lie along those fault lines and this may not be merely due to chance, but they may have been placed there deliberately.The Temple of Apollo at Delphi with Mount Parnassus in the Background
The Temple of Apollo at Delphi with Mount Parnassus in the BackgroundCourtesy Wikimedia Commons

For example, the Oracle at Delphi has been given a geological explanation. The Delphi Fault (running east-west) and the Kerna Fault (running SE-NW) intersect near the oracular chamber in the Temple of Apollo. In that area, bituminous limestone (i.e. limestone containing bitumen, a tarlike deriviative of petroleum) has a petrochemical content as high as 20%. Analysis of spring water in the area showed the presence of hydrocarbon gases, such as ethylene. Geologists have hypothesized that friction from fault movement heats the limestone, causing the petrochemicals within to vaporize. It has been suggested that exposure to low levels of the sweet-smelling gas ethylene would induce a trance, or euphoric state. Could the naturally occuring ethylene account for the strange, prophetic behavior of the Pythia (the priestess at the Temple of Apollo)?

The Delphi research is certainly persuasive, and received favorable coverage in the popular press and Scientific American, but it has come under criticism. Critics argue that the concentrations of ethylene identified by the researchers would not be sufficient to induce a trance-like state, and thus the connection to the mantic behavior of the Pythia is dubious.

Report: Geomythology: Geological Origins of Myths and Legends
Article: Breaking the Vapour Barrier: What Made the Delphic Oracle Work?
Report: Oracle at Delphi May Have Been Inhaling Ethylene Gas Fumes

Related Report: Earthquake Faulting at Ancient Cnidus, SW Turkey

Folded Rock North of Loch Melfort in Scotland
Folded Rock North of Loch Melfort in ScotlandCourtesy Anne Burgess

A rock mass visible at the surface is named an "outcrop" by geologists. Most of these outcrops are made of a single, homogenous kind of rock (e.g. basalt) but in many cases rocks are layered, fractured, cleaved, or show more complicated patterns on their surface. At high temperatures and pressures inside the earth, rocks can move slowly, or can fracture creating fault planes. Outcropedia is a website meant to show a collection of such outcrops.

Outcropedia is the brainchild of three structural geologists : Cees Passchier, Mark Jessell, and Hermann Lebit. It uses a GoogleEarth template, and by clicking on a datapoint, you can see a photograph or drawing with explanatory text. Many of the outcrops included are in remote areas of planet Earth. Outcropedia welcomes new submissions, so if you have an image of an outcrop, submit it for addition!

May
25
2005

The United States Geologic Service has launched a website which shows the probability of an earth-shaking event in any spot for California over the next 24 hours. The model is most useful in predicting aftershocks — small tremblers that follow a large quake. Those large quakes remain almost impossible to predict. But knowing if an aftershock is due will help Californians prepare their homes and keep damage to a minimum.

Earthquakes occur when two pieces of the Earth's crust collide, divide, or scrape past one another. The dividng line between two such pieces is called a fault line. Many fault lines run through California, so they have lots of earthquakes. Minnesota has no fault lines, so earthquakes here are very rare.

Read more about earthquake forecasting