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Geologic Hazards
Video: Emergency Response to Nile Valley Landslide, WA SR 410 PDF Print E-mail
Written by Randy Post   
Monday, 24 May 2010 22:01

In October of 2009, a massive landslide in the Nile Valley, near Yakima, Washington, took out a portion of Washington SR 410 and impacted the Naches River as well. This video from WSDOT shows what emergency response was required to get temporary traffic restored on a detour and get a more permanent detour constructed.

Last Updated on Monday, 24 May 2010 09:05
 
City of Newport, Oregon Considering Strict Geologic Hazard Ordinance PDF Print E-mail
Written by Randy Post   
Wednesday, 19 May 2010 12:48

2786206520_082e9456fc_m[1] Geologic Hazards in Newport, Oregon will need to be disclosed to prospective property buyers, and the necessary geologic reports will need to be filed if a proposed City ordinance is adopted. But this will also require the property owner to sign a “Geologic Hazard Disclosure and Liability Waiver” form that would release the City from liability associated with the geologic hazards. The zones where this would be required are based on Oregon Department of Geology and Mines (DOGAMI) geologic hazard maps which have so called “red zones” which denote “active” and “high” hazard zones. These are primarily areas on the coast and the red zones are eroding as a rate of up to 1/3-ft per year. (Source: Newport News Times, Photo: Yaquina Bay Bridge, Newport, Oregon by kightp on Flickr.

Last Updated on Wednesday, 19 May 2010 12:49
 
Landslide on Quick Clay near Montreal, Quebec, Canada PDF Print E-mail
Written by Randy Post   
Thursday, 13 May 2010 12:46

What was initially reported in the media as a sinkhole in the area of St. Jude, Quebec, northeast of Montreal, appears to be a landslide caused by so called quick clay. This particular formation, the Leda Clay, is well known for these types of failures. Tragically, a family of 4 was killed while watching TV in their basement when the slide occurred. A collection of media and blog coverage on the event is presented below.

St. Jude, Quebec Quick Clay Landslide Links

 

 
Landslide Covers Freeway, Kills at Least 4 in Taiwan PDF Print E-mail
Written by Randy Post   
Thursday, 29 April 2010 13:09

Landslide covers Freeway 3 in TaiwanLast Sunday, April 25, 2010 a major landslide covered a 300-m plus stretch of Taiwan’s National Freeway No. 3, killing at least 4 people and burying three cars and destroying a bridge. The estimated volume of the slide is 200,000 cubic meters (262,000 C.Y.). [Photo by Reuters]

The failure mode appears to be a dip-slope type failure, possibly as shallow as 20-degrees and according to the MSNBC article, the failure was preceded by “days of rain” so the slope was likely at least partially saturated.

From Google Earth photos seen at Dave’s Landslide Blog, it appears the failure occurred on an engineered cut slope. And a Taiwan News article indicated that there were some kind of anchors stabilizing the slope, but there were comments regarding possible corrosion and age of the ground anchors. Likely the investigation into the failure will center around this issue.

Initial rescue efforts consisted of some 45 excavators and 800 people. The search and rescue efforts continue and as-of Thursday 4/29, four bodies had been recovered.

Additional Info and Links

Last Updated on Thursday, 29 April 2010 13:17
 
Mt. Soledad Landslide Lawsuit Finally Settled by City of San Diego PDF Print E-mail
Written by Randy Post   
Tuesday, 27 April 2010 00:17

A nearly three year battle between homeowners affected by the 2007 landslide on Mt. Soledad Road in a La Jolla neighborhood is now over. I first blogged about this event shortly after it happened as well as during some of the early investigations and remediation work and the legal affairs. Then in October of 2009, a California Superior Court Judge ruled in favor of the City of San Diego in a lawsuit by homeowners, agreeing with the City that the landslide was a result of the local geology (paleo landslide) and not the actions of the City.

Last week the San Diego City Council voted to approve a $284,000 settlement over the 2007 landslide that ensured the homeowners would not file an appeal. There were originally 65 homeowners that sued the City, and San Diego spent over $6 million in outside legal fees fighting the suits. That’s in addition to the roughly $20 million it paid for emergency cleanup and stabilization consisting of shear pins and drains.

Last Updated on Tuesday, 27 April 2010 00:17
 
What Makes a Sinkhole a Sinkhole? PDF Print E-mail
Written by Randy Post   
Friday, 23 April 2010 16:12
A subsidence incident or sinkhole on First Street in San Francisco, blocking traffic to the Bay Bridge. By telstar on Flickr.

The Florida Geological Survey probably deals with more sinkholes than most agencies. The most frequent geologic cause of sinkholes is dissolution of limestone and other soluble rocks and the collapse of the soil cover over them. However, there are other events that are often called “sinkholes” by the media and frequently civil engineers even if they are not a geological sinkhole. The FGS uses the term “subsidence incident” to denote all types of sinkhole phenomena and only after investigations to they formally call them sinkholes. Here’s how they define sinkhole on their website: (Photo of a “subsidence incident” on First Street in San Francisco by telstar on Flickr)

Sinkholes are closed depressions in areas underlain by soluble rock such as limestone, dolostone, gypsum, or salt.  Sinkholes form when surface sediments subside into underground voids created by the dissolving action of groundwater in the underlying bedrock.

Other subterranean events can cause holes, depressions or subsidence of the land surface that may mimic sinkhole activity. These include subsurface expansive clay or organic layers which compress as water is removed, collapsed or broken sewer and drain pipes or broken septic tanks, improperly compacted soil after excavation work, and even buried trash, logs and other debris. Commonly, a reported depression is not verified by a licensed professional geologist to be a true sinkhole, and the cause of subsidence is not known. Such an event is called a subsidence incident.  The Florida Geological Survey maintains and provides a downloadable database of reported subsidence incidents statewide.  While this data may include some true sinkholes, the majority of the incidents have not been field-checked and the cause of subsidence is not verified.

Last Updated on Friday, 23 April 2010 09:23
 
Sierra El Mayor (Baja) 7.2 Magnitude Earthquake PDF Print E-mail
Written by Randy Post   
Wednesday, 07 April 2010 12:17

A magnitude 7.2 earthquake in the Baja region of Mexico on April 4, 2010 (Easter Sunday) caused significant damage in the towns of Mexicali and Calexico and was felt as far away as Phoenix, San Diego and Los Angeles. Here are several new articles and blog posts on the event.

Last Updated on Wednesday, 07 April 2010 12:22
 
I-70 Glenwood Canyon Rock Slide Damages Road, Bridge PDF Print E-mail
Written by Randy Post   
Monday, 08 March 2010 23:46

Glenwood Canyon I-10 Rock slide, 2010 Colorado governor Bill Ritter declared a disaster emergency Monday after a slide in Glenwood Canyon struck near midnight Sunday. It was located near Hanging Lake Tunnel, spot of a 2004 rockfall event that damaged a portion of cut and cover tunnel and required some innovative repair techniques. (Photos by CDOT via 9 News)

No injuries were reported, but the slide did some significant damage to median barriers, pavement, guardrails and even a bridge. Boulders up to 10-ft in diameter and up to 66-tons in weight fell into the westbound lanes. But perhaps the most impressive damage was the large hole or possibly holes that it punched through the bridge.

Glenwood Canyon I-10 Rock slide, 2010Repairs are currently underway, but the freeway will likely remain closed for some time. The closest detour is on the order of 200-miles.

I-70 Glenwood Canyon Rock Slide Links

Last Updated on Monday, 08 March 2010 23:47
 
Dozens of Sinkholes in Plant City, Florida after Farmers Pump Extra Water Trying to Protect Crops from Bitter Cold PDF Print E-mail
Written by Randy Post   
Sunday, 07 March 2010 23:55

60-ft plus deep sinkhole in Frostproof takes a carport, threatens a houseIn early January of this year, Florida experienced some unusually cold temperatures that forced Plant City area strawberry farmers to pump extra groundwater to try to protect their crops. Over the course of about 11 days, the groundwater table in areas of Plant City was lowered by as much as 60-ft.

Almost immediately as many as 80 sinkholes began opening up around that region. Including ones that jeopardized a 500,000-gallon water tower, several that shut down an elementary school and numerous ones that shut down roads and highways and affected individual property owners. Around 20 local homeowners were left homeless after sinkholes left their house uninhabitable. For comparison, based on data from Florida Department of Environmental Protection’s Sinkhole Database for the period of 1998 to 2008 (the last year for which data is available), 77 sinkholes were reported to have opened up in Polk, Pasco and Hillsborough counties combined.

Local officials are seeking help from the State and FEMA to cover the estimated $3 million in damages.  That figure is double what Plant City received from FEMA for the particularly bad 2004 hurricane season. And that dollar amount does not include what individual homeowners and property owners will be seeking from their insurance carriers. (Photos by Tampa Bay Online)

Read on for maps of Plant City sinkhole locations and more information.

Last Updated on Monday, 08 March 2010 00:28
 
Video: Rockslide on Highway 96 in Northern California PDF Print E-mail
Written by Randy Post   
Sunday, 07 March 2010 22:30

A short 25-second video showing an impressive rock slide event. Credit to Dave’s Landslide Blog.

Rock slide on Hwy 96 in Northern California near the Humboldt/Siskiyou County line. from Paul Hailey on Vimeo.

Last Updated on Saturday, 06 March 2010 21:31
 
Chile Earthquake Links - March 1, 2010 PDF Print E-mail
Written by Randy Post   
Monday, 01 March 2010 12:24

A few interesting links related to the Chile Earthquake. Over the next days and weeks, I will try to highlight interesting news and blog posts related to this event.

 
Chile Earthquake 2010 – Magnitude 8.8 PDF Print E-mail
Written by Randy Post   
Monday, 01 March 2010 01:15

Chile Earthquake 2010 - Destroyed appartment building A magnitude 8.8 earthquake struck Chile on Saturday, centered about 200 miles southwest of the capital, Santiago and 70 miles north-northeast of Concepcion, one of the worst hit areas. According to the USGS event page, it occurred at about 3:30AM local time, with the epicenter about 21-miles below the ground, on the boundary between the subducting Nazca plate and the South American Plate (if you remember your plate tectonics). The earthquake prompted tsunami warnings around the Pacific Rim but the waves that materialized were relatively minor. As of Sunday night, the death toll for this earthquake is around 700. (Photo from the Daily Mail)

Chile Earthquake 2010 - Collapsed freeway According to Geology.com, this earthquake was the 5th most powerful ever recorded. The most powerful earthquake ever recorded was the 1960 earthquake in Chile at 9.5 magnitude. Surprisingly, there was not as many casualties in the immediate vicinity of the 1960 quake as you would expect for one of that size.  The reason is that it occurred in the middle of the day and was preceded by a powerful foreshock that frightened people out of buildings, many of which were leveled when the main quake hit. However, some 2 million people were left homeless.

The resulting tsunamis from the 1960 quake were responsible for perhaps a larger number of casualties, including 61 people killed in Hawaii with wave amplitudes of 35-ft. 185 people in Japan were killed by the tsunamis, and 32 people in the Phillipines. Waves up to 1.7-m high were measured at locations along California’s coast.  All of these things put into perspective why they called for a tsunami warning around the pacific rim after this earthquake.

Last Updated on Monday, 01 March 2010 01:15
 
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