Experience the sound of a powerful Earthquake

Strong Motion seismometer that measures accele...

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Thanks to the great service of USGS, we are able to share the sound of a couple of earthquakes to our readers.
As every earthquake has it’s own fingerprint, the sound  going together with it can be seriously different.  Depending on the  Magnitude, rock material, fault lines, etc. the frequency can be low or high and the sound can be short or rolling.

It may be easier to hear the small triggered earthquakes than it is to see them. The Landers earthquake is far from the seismometer so most of its high frequencies have died away before the waves reach the seismometer. But the small earthquakes have small fault areas and therefore produced high frequency energy and because they are near the seismometer this energy has not died away.

Listen to the seismogram recorded at the Long Valley Caldera and see if you can hear the small earthquakes (high frequency bursts) despite the low rumble of the distant large earthquake. Click the sideways triangle (or play button) to hear the sound.

If you are having trouble picking out the small nearby earthquakes, listen for the two very close to the end and then listen to the seismogram again.

Listen to the seismogram recorded at the Long Valley Caldera and see if you can hear the small earthquakes (high frequency bursts) despite the low rumble of the distant large earthquake. Click the sideways triangle (or play button) to hear the sound.

Long Valley Caldera Seismogram

Earthquake sound 1

If you are having trouble picking out the small nearby earthquakes, listen for the two very close to the end and then listen to the seismogram again.

Here are two more seismograms of the Landers earthquake. One is recorded at Parkfield near Paso Robles and the other is recorded at the Geysers north of San Francisco. Only one of these areas had small earthquakes triggered by the Landers event. Can you tell which one?


Parkfield Seismogram

Earthquake sound 2

Geysers Seismogram

Earthquake sound 3

Your earthquake “FELT” report is of very big importance for science

Earthquake-report.com will from now on encourage FELT reporting from his readers.

Most people are not aware of the importance of their cooperation in reporting their FEEL experiences to the science organizations. The best developed is certainly USGS who gets a big number of felt reports for many earthquakes.

EMSC-CSEM is the European counterpart of USGS and is also a very important agency who does follow earthquakes worldwide and makes outstanding reports with their scientific data.

From now on, Earthquake-report.com will put a FEEL link behind every earthquake in order to have the form always at hand if you have experienced the earthquake yourself.
If you opt to describe what you felt (in your local language !) your individual story can be found on the internet in the EMSC-CSEM website.

Why a FELT report ? Does science doesn’t know it all ?
Earthquake science does know a lot but far from everything.
Predictions are far from being accurate as no scientist will know when and how strong an earthquake will strike. The places above fault lines are better and better known, but nobody knows when the rope will break apart.
The way people are experiencing an earthquake is also totally different with each earthquake.  Depending on the place where they live, the scientific components of a quake, the house they live in, etc every earthquake is experienced differently.
At earthquake-report.com we have noticed continuously that users from our QUAKESOS iPhone Application react totally differently as we sometimes expect. Smaller magnitudes are sometimes experienced as a more powerful earthquakes and bigger Magnitudes are hardly noticed.
Filling up your FEEL form will give science a bigger understanding of the human impact versus raw earthquake data.

The forms are rather extensive, but we encourage filling them up as good as possible as every detail is important for scientists.

How to easily strengthen Haiti earthquake-prone structures ?

Civil engineers studying the effects of Haiti’s devastating earthquake have concluded that a relatively simple system could be used by officials to quickly decide how to modify existing buildings and construct new ones that would better withstand future quakes.

The system, which uses a priority index to rank reinforced concrete buildings according to their seismic vulnerability, originally was developed in Japan and later adapted for use in Turkey by researchers at Purdue University.

A recent study has shown that the system also is applicable to Haiti. The indexing system could be used to identify which buildings need to be strengthened and to guide the construction of new structures, said Santiago Pujol, a Purdue assistant professor of civil engineering.

The researchers surveyed 170 buildings damaged in the January 2010 earthquake. About 40 percent of the buildings were heavily damaged, and findings showed that about 90 percent of those damaged structures would have been classified as vulnerable if the system had been in use.

“What the index tells you is that for a given-size building, the smaller the columns and the fewer the walls between the columns, the more likely the building is to have severe damage,” Irfanoglu said. “Its strength is in its simplicity and the ease of measuring it in the field.”

The index is a ratio of the combined cross sectional areas of all of the ground-story columns and walls compared to a building’s total usable floor area.

A common flaw seen in the buildings is referred to as “captive columns,” where a wall is attached to a column but does not extend as high as the column, leaving a portion of the column unsupported. This configuration, often seen in school buildings, results in severe damage to the unsupported segment of the columns.

The flaw is widespread in Haiti, as well as China, Latin America, Turkey and many other countries, but buildings could easily be strengthened by reconfiguring the “partial-height” walls, Pujol said.

“The Haitians need to concentrate on fixing the buildings that have smaller columns and fewer walls, and there are many such buildings still standing,” he said. “Secondly, they should modify the buildings that have captive columns and ban the use of captive columns in new buildings.”

About 60 percent of the 170 buildings had captive columns.

“We are sharing these findings with engineers at Haiti’s Ministry of Public Works, and we hope they will be interested in using it,” Irfanoglu said.

Click here to read the full original article from Perdue University

Article Courtesy : Perdue University

Christchurch Earthquake Damage Map with ‘damage and testimonies’

Earthquake-Report.com is always in for “added value” articles from local publishers.
We came across a fantastic initiative from “The Press – Stuff.co.nzwho had the idea of bundling testimonies from people living in the earthquake area on a google map. With colored buttons viewers can click on each of the buttons and read the story behind the button.

Most damage seem to have occurred in the old city center of Christchurch, although other parts of the area were also hurt.

If you click on the map, you are linked to the big interactive earthquake map from the publisher.
Congratulations from Earthquake-Report.com for this great initiative.

How is earthquake data measured, computed and published ?

Geonet, The New Zealand governmental office who publishes earthquake information, released a very good describing article how an earthquake is measured, monitored, computed etc.
Earthquake-Report.com has a constant interest in explaining the background of earthquake numbers for his readers. We hope that this article will clarify a number of issues concerning earthquakes.

To make rapid locations of earthquakes GeoNet operates a country-wide network of seismic stations that transmit their data to the GeoNet Data Management Centre (DMC) where it is analysed by automated processes. If the automated processes detect an earthquake the Duty Response Team is notified and if the Duty Officer confirms that the earthquake is real and significant, the earthquake information is released.

The seismic stations operated by GeoNet consist of a seismometer and a seismograph. A seismometer is a sensitive instrument that generates a small electrical current in response to ground shaking. The electrical current is digitised by the seismograph and transmitted continuously to the DMC in real time. This digital recording of ground shaking is the raw data used to make earthquake locations. The seismic stations are supplemented by a network of strong-motion seismographs, which only transmit data whenever they detect a higher level of shaking, typically from earthquakes that will have been felt by the public.

The real-time seismic data is received by the DMC data reception computers located at Avalon (Lower Hutt) and Wairakei (near Taupo) and analysed automatically for possible earthquakes. The computer processes look for ground shaking that is distinct from the normal background activity (such as that caused by weather and oceans) and may be associated with an earthquake. These occurrences are called detections. If a detection is deemed significant, then the relevant portion of the data is parcelled up and sent to the DMC data analysis computers. They store all the detected earthquake data, grouping the detections from different stations into earthquake data sets. The detections are examined for P (primary) and S (secondary) wave arrivals from the earthquake, and the times of these arrivals are inverted against seismic velocity models for the earth to yield the best location for the event. The magnitude of the earthquake is determined at a station by measuring the maximum amplitude of the seismic signals, and relating them to the distance of the station from the event, together with the characteristics of the seismometer and seismograph. The magnitudes from all available stations are then averaged to give an overall value for the event.

It also provides locally recorded data from global earthquakes to the International Seismological Centre in the United Kingdom, and preliminary earthquake information to the National Earthquake Information Center, part of the United States Geological Survey responsible for locating major earthquakes worldwide. The waveform data and the located hypocentres are freely available to the worldwide community of researchers through the Resources section of this website.

Courtesy Geonet and GNS Science – Link to the original article of Geonet – GNS Science

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