Know Your Earthquakes

Earthquake Chicago |Illinois Earthquake In Chicago - An earthquake is characterised by vibrations generated in the crust of the Earth during the sudden rupture of rocks that accumulated elastic strain and then rebounds. The vibrations produced can vary from hardly perceptible to appallingly damaging. Earthquakes have the potential of releasing energy more than a thousand times greater than the world's first atomic bomb.

Earthquake Chicago - There are three general types of earthquakes being recognised: volcanic, tectonic, and artificially produced. Among the three, the tectonic type is by far the most destructive, and this same type of earthquake establish specific intricacies for scientists attempting to build on methods of predicting them

Earthquakes bring about several aspects of concern to the people residing in these so-called seismically active areas. This natural calamity can produce immense loss of life by annihilating structures like bridges, buildings, dams, and other infrastructures and it can even start devastating landslides.

Another fatal result of earthquakes is the creation, oftentimes by undersea vibrations, of so-called tidal waves. Since such waves are not related to the tides, they are more appropriately called as seismic sea waves or tsunamis. These high rising walls of water have smacked inhabited coastal areas with such fierce rage that whole towns have been damaged.

Seismologists, the scientists who study earthquakes, have created two measurement scales that would enable them to categorise earthquakes quantitatively. First is the Richter scale, which was coined in honor of the American seismologist Charles Francis Richter. It gauges the energy given off at the focus of a quake. Its scale ranges from 1 to 9. One being the weakest and 9 as the most destructive.

The other scale is the Mercalli scale that was introduced during the start of the 20th century by the Italian seismologist Giuseppe Mercalli. It measures the intensity of shaking with gradations from I to XII. The Mercalli rating depends on the site where the measurement was taken since the seismic surface effects decrease with distance from the focus of the quake. Intensity I on the Mercalli scale is described as an earthquake perceived by very few people, while intensity XII is designated to a disastrous occurrence that brings about full-blown devastation.

Efforts on forecasting the time and place earthquakes will take place have had some positive accomplishments in recent times. At the moment, countries like Russia, Japan, China, and the United States are the nations putting in significant efforts to support earthquake research. Several predicted occurrences of earthquakes date back in 1975 when the Chinese forecasted a 7.3 Richter scale magnitude quake at Haicheng, that made them evacuate less than a hundred thousand inhabitants only a couple of days before the quake actually happened which damaged or destroyed 90 per cent of the city's buildings. Low-magnitude vibrations or tremors or foreshocks are some indicators of an incoming earthquake. Some other possible hints being inspected are bulging or titling of land surfaces and modifications in the magnetic field of the earth, in the depth of wells, and even in behaviour of animals.

Powerful quake off California

Eureka Earthquake,A 5.9-magnitude earthquake rattled northwest Mexico near the California border on Wednesday, the United States Geological Survey said.

The temblor's epicentre was in Mexico's Baja California, about 171 kilometres east of the border city of Tijuana, the USGS said.

There were no early reports of injuries or damage due to the quake, which struck at 1848 GMT and was followed by a 4.9 aftershock in the same area minutes later, according to the USGS. - AFP/de

A powerful 6.5-magnitude earthquake struck off the coast of northern California Saturday, leaving no victims and causing minor damage, officials said.

The US Geological Survey reported that the tremor occurred 22 miles (35 kilometers) west of Ferndale and 224 miles (360 kilometers) northwest of Sacramento, at a depth of nine miles (16 kilometers).

The quake hit at 4:27 pm (0027 GMT Sunday) and was followed by a series of four aftershocks measuring 3.7, 3.8, 3.5 and 3.6 on the open-ended Moment Magnitude Scale.

There were no initial reports of injuries.

The National Oceanic and Atmospheric Administration said a tsunami was not expected.

"Oh yeah, it shook," Ferndale volunteer fireman Manuel Enos told AFP, "Windows broke or popped out of storefronts."

Local media also reported a brief power cut, ruptured gas lines and damage to Ferndale's city hall building. Pictures posted on the Twitter website showed broken shop windows, toppled shelves in stores and products strewn all over the floor.

However Lori Newquist, a spokeswoman for the California Emergency Management Agency, told ABC television the damage was not serious.

"At this point, no major damages have been reported," she said. "We are monitoring the situation very closely".

However, local media reports said about 18,000 customers were without electricity and telephone service was spotty throughout the affected area.

The Los Angeles Times reported the initial jolt was felt as far away as San Francisco.

"We've been through a lot of earthquakes but I can't recall there ever being any this bad," Sandra Hall, owner of Antiques and Goodies in nearby Eureka, told the Times.

She said the quake moved her store in all directions, with broken lamps, dishes and clothing now littered across the shop. Two women took cover under a table and a couple ran out of the main entrance.

Sandra Lewis, a resident of Eureka, called the seismic event "really scary.

"It felt like my house jumped up by the foot," she told ABC. "I could see it. The TV started waving back and forth, there was some kind of a rumbling noise, things were falling off my shelves and all my picture frames are over."

Sarah Hernandez, another Eureka resident, said she felt "shaken and scared."

She said her home had suffered no structural damage, but some of her personal belongings were broken. In addition, there was no power in her neighborhood and the telephone service was unstable, Hernandez pointed out.

The quake occurred in an area known to seismologists as the Mendocino Triple Junction where three tectonic plates meet and cause frequent seismic events.

"This is an earthquake that happened to be in a part of California where we have a lot of earthquakes," said Tom Brocher, a specialist with the US Geological Survey. "This is not a surprise."

He added that Saturday's tremor was "a little bit bigger than most of our earthquakes out there, but it's certainly in the range that we see up there."