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Disseminating Information: Twitter vs. USGS on the Sichuan Earthquake
Posted on Thursday, May 15, 2008 @ 3:05 pm by Dave Schumaker
On Sunday evening, noted Bay Area tech blogger Robert Scoble, became one of the first people in the western hemisphere to find out about a large earthquake in China. He reposted a message he received on his Twitter account about the breaking news and within minutes, thousands of people around the world were aware that something had just happened.
Scoble’s Twitter message immediately after the Sichuan earthquake.
Later that evening, Scoble wrote a message on his blog, explaining how Twitter beat the USGS with information about the earthquake and sharing his amazement at learning about news as it happened on Twitter. Rory Cellan-Jones, a technology blogger for the BBC News, even went on to imply that this could mark Twitter’s “coming of age,” and establish its importance in disseminating information about major news events.
Does this really establish Twitter’s importance as a source of news? And how does this compare with the response time and information available from the USGS?
More after the jump. (more…)
Sichuan Quake Ruptured in 2 Stages
Posted on Thursday, May 15, 2008 @ 11:16 am by Dave Schumaker
According to Yuji Yagi, a seismologist at Tsukuba University in Japan, Monday’s Sichuan earthquake in China ruptured in 2 stages.
Yuji Yagi, a seismologist at Tsukuba University, said data show the 155-mile Longmenshan Fault tore in two sections, the first one ripping about seven yards, followed by a second one that sheared four yards.
Despite the two-stage quake, which he estimated lasted for about two minutes, it was the shallowness of the epicenter - only 6 miles - that contributed most to the temblor’s destructive power, he said.
“The damage was very severe because the quake’s epicenter was shallow, and the quake occurred in densely populated areas,” said Yagi.
The AP article doesn’t have many details, but it sounds like they are talking about a phenomenon that is similar to a “cascading earthquake,” which happens when rupture on one fault starts a chain reaction that causes a simultaneous rupture on a nearby fault, in essence, creating two earthquakes.
I thought we’ve talked about cascading earthquakes before on Geology News, but looking through the archives, it appears I have never posted about them here. I did briefly mention them on Metafilter back in 2006 (and referenced the same article above).
James Dolan of the University of Southern California in Los Angeles says that the work “reinforces our sense that earthquakes on one fault can and have triggered earthquakes on another.” He has dug trenches on the Cucamonga fault, showing that the fault breaks every 500 to 1,000 years, evidence that the USGS team used. The Sierra Madre ruptures every 5,000 to 10,000 and the San Jacinto every 100 to 300 years. An event cascading across all three would be the region’s “doomsday quake,” Dolan says. “If this ever happens, it’s incredibly infrequent.”
The doomsday event Ralph Archuletta, a seismologist at the University of California at Santa Barbara, imagines is the San Andreas Fault failing along with a big thrust fault, which might be hidden in the valley. But he agrees that the three faults acting alone, which are closer to metropolitan areas than the San Andreas, would be worrisome. “A 7.5-magnitude earthquake near a populated area is not insignificant — whether or not it implies a Denali-style event,” he says.
Recording of the Sichuan Earthquake
Posted on Tuesday, May 13, 2008 @ 9:05 am by Peter Polito
Two hosts from NPR’s afternoon show, All Things Considered, were in the Sichuan Province when the recent earthquake struck. Melissa Block and Robert Siegel were in Chengdu, approximately 60 miles from the epicenter. Melissa Block was in the middle of the interview when the earthquake struck. The audio bit of the interview is available here (just below the photo gallery). About 40 seconds into the recording you can hear the building start to shake, she ran outside narrating what she was looking at as she ran. If you listen closely you can hear a gap in the shaking between the P and S waves. Also, note the time when the shaking starts and when she states that the shaking is subsiding, it is well over a minute.
Having never experienced a quake of this magnitude it is quite surreal to hear. And living in the Bay Area it makes me want to check my earthquake kit.
M7.8 Earthquake in Central China
Posted on Sunday, May 11, 2008 @ 10:28 am by Dave Schumaker
A magnitude 7.8 earthquake struck central China earlier today. It was centered in the Sichuan province, about 1500 kilometers from Beijing. Shaking was felt as far away as Beijing. CNN reports that at least 10,000 people are feared dead. The earthquake was rather shallow (the focus being located only 10km beneath the surface).
Source: USGS
The following is a release by the United States Geological Survey, National Earthquake Information Center: An earthquake occurred 90 km (55 miles) WNW of Chengdu, Sichuan, China and 1545 km (960 miles) SW of BEIJING, Beijing, China at 12:28 AM MDT, May 12, 2008 (2:28 PM local time in China). The magnitude and location may be revised when additional data and further analysis results are available. There have been no reports of damage.
Source: Reuters
From CNN:
At least six more earthquakes — measuring between 4.0 and 6.0 magnitudes — happened nearby over the three hours after the initial quake at at 2:28 p.m. local time (0728 GMT), the USGS reported.
advertisementA spokesman for the Beijing Olympic Committee said no Olympic venues were affected by the earthquake. The massive Three Gorges Dam — roughly 600 km east of the epicenter — was not damaged, a spokesman said.
The earthquake was also felt in Hong Kong, Shanghai, Taiwan, and as far away as Hanoi, Vietnam, and Bangkok, Thailand, according to the Hong Kong-based Mandarin-language channel Phoenix TV.
Update: The latest estimates say that over 10,000 have been killed. And it will probably be significantly higher than that as rescuers reach cities that have been cut off due to damages to roads and lines of communication. From CNN: It reported that authorities were yet to reach Wenchuan County — which sits at the epicenter of the 7.9-magnitude earthquake with a population of about 112,000 — because of damage to roads.
[Via USGS]
M4.7 near Reno, Nevada
Posted on Sunday, April 27, 2008 @ 12:37 pm by Peter Polito
Late Friday night Mogul, NV (just west of Reno) was struck by a M4.7. While a M4.7 earthquake is not terribly large, it was a very shallow quake causing items to fall off grocery shelves, minor rock falls in the surrounding hills, and some of the taller casinos to sway. This quake is the largest thus far in a swarm that began approximately two weeks ago causing seismologists at University of Nevada Reno to issue a statement warning residents of a heightened probability of a larger earthquake.
Source: University of Nevada Reno.
Following an earthquake of this size there is a small increase in the probability of a larger magnitude earthquake in the west Reno area. Citizens should also be aware of the possibility of strong aftershocks from this evenings Magnitude 4.7. Mogul-Somersett residents should expect to feel aftershocks of this earthquake for some time. It cannot be determined if this evenings Magnitude 4.7 earthquake will be the largest earthquake of the 2008 Mogul-Somersett earthquake sequence
The Seismological Laboratory at UNR has posted some terrific products related to this swarm which can be found on their website. The graph below shows clearly how the recent swarm is not just background noise but a true signal:
Source: University of Nevada Reno.