RENO, Nev. - Scientists at the University of Nevada, Reno are scrutinizing seismic readings and studying damage at residents' homes to try to figure out what's happening beneath the earth's surface under a northwest Reno neighborhood rocked by a seemingly endless string of earthquakes.
What they can't say is whether the hundreds of temblors that have rattled the area for two months — the largest a magnitude 4.7 Friday night — are subsiding or a prelude to bigger things to come.
"You're not going to get an earthquake prediction today," John Anderson, director of Seismology Laboratory at the University of Nevada, Reno, said Tuesday during a briefing with Gov. Jim Gibbons and emergency managers on the seismic activity.
Scientists are calling the swarm of temblors that began Feb. 28 the "Mogul earthquake sequence", in reference to the neighborhood where hundreds of mostly minor earthquakes have occurred.
But the shaking is unusual, seismologists say, because the intensity of the quakes has increased over the past few weeks. Generally, earthquakes tend to occur and are followed by smaller aftershocks.
In this case, the earth's rumblings have continued unabated, with barely negligible bumps occurring often minutes apart, followed by occasional larger shakers.
It's impossible to know if the temblors are foreshocks of a bigger quake to come, or aftershocks of what has been, experts said.
Up until April 15, sizable quakes that could be felt were occurring about once every third day.
Then, the rate increased, with about three, 2.0 or larger incidents occurring daily.
On April 24, when the first 4.2 quake was registered, "all of a sudden we were seeing 20 (of the magnitude) 2s and larger per day," said state geologist Jon Price.
"This is an exceptionally vigorous sequence of earthquakes," Price said.
During the past week alone, more than 500 occurrences have been recorded.
Most recently, two measuring 3.1 and 3.2 in magnitude occurred around 11 p.m. Monday. Another 3.1 was recorded at 9:15 a.m. Tuesday.
The largest so far was a 4.7 quake that was registered at 11:40 p.m. Friday. It was preceded 11 seconds earlier by a 3.3 quake, and followed 3 minutes later by one registering 3.4.
The temblors sent goods flying off shelves, cracked walls, broke glass and collapsed part of a water flume west of Reno. There were no injuries.
They are mostly shallow, occurring just beneath the surface to within a mile or two.
"Shallow makes us believe this is absolutely not volcanic," Price said.
Mapping of the quakes shows they are clustered around the Mogul and Somersett neighborhoods in northwest Reno, in an area about 2.5 miles long and 1/3 of a mile wide.
Craig dePolo with the Nevada Bureau of Mines and Geology, said he understands the anxiety of residents who have lived with the persistent shaking.
"What's going on is extraordinary," he agreed. "People are being needled by little earthquakes ... for months."
"And the best we can say is we don't know what going to happen."
DePolo, who said he's been through many earthquakes, acknowledged that he, too, is "a little nervous."
The governor and emergency managers urged residents to be prepared by strapping down water heaters or any heavy items that could fall and injure people and to have first aid and food provisions on hand.
Frank Siracusa, head of the Nevada Division of Emergency Management, said state, regional and local agencies train constantly for disasters and have been in daily contact.
"I'd like to say we're prepared, but we can never be too prepared," he said.
The governor said he's "very concerned about the safety of the public," and stressed that residents need to be prepared to minimize risk in the event of a disaster.
Gibbons, himself a geologist, said the earth's movement is what makes the mountains and Nevada landscape so special.
"I find it fascinating about our earth and how it continually evolves over time," he said.
But with Nevada being the second most seismically active state in the continental U.S., he echoed the advice of experts who said large earthquakes are inevitable.
"At some point ... we are going to have a magnitude 6 or 7," Gibbons said.
Earthquake magnitudes are calculated according to ground motion recorded on seismographs. An increase in one full number — from 5.5 to 6.5, for example — means the quake's magnitude is 10 times as great.
A quake with a magnitude of 6 can cause severe damage, while one with a magnitude of 7 can cause widespread, heavy damage.
What they can't say is whether the hundreds of temblors that have rattled the area for two months — the largest a magnitude 4.7 Friday night — are subsiding or a prelude to bigger things to come.
"You're not going to get an earthquake prediction today," John Anderson, director of Seismology Laboratory at the University of Nevada, Reno, said Tuesday during a briefing with Gov. Jim Gibbons and emergency managers on the seismic activity.
Scientists are calling the swarm of temblors that began Feb. 28 the "Mogul earthquake sequence", in reference to the neighborhood where hundreds of mostly minor earthquakes have occurred.
But the shaking is unusual, seismologists say, because the intensity of the quakes has increased over the past few weeks. Generally, earthquakes tend to occur and are followed by smaller aftershocks.
In this case, the earth's rumblings have continued unabated, with barely negligible bumps occurring often minutes apart, followed by occasional larger shakers.
It's impossible to know if the temblors are foreshocks of a bigger quake to come, or aftershocks of what has been, experts said.
Up until April 15, sizable quakes that could be felt were occurring about once every third day.
Then, the rate increased, with about three, 2.0 or larger incidents occurring daily.
On April 24, when the first 4.2 quake was registered, "all of a sudden we were seeing 20 (of the magnitude) 2s and larger per day," said state geologist Jon Price.
"This is an exceptionally vigorous sequence of earthquakes," Price said.
During the past week alone, more than 500 occurrences have been recorded.
Most recently, two measuring 3.1 and 3.2 in magnitude occurred around 11 p.m. Monday. Another 3.1 was recorded at 9:15 a.m. Tuesday.
The largest so far was a 4.7 quake that was registered at 11:40 p.m. Friday. It was preceded 11 seconds earlier by a 3.3 quake, and followed 3 minutes later by one registering 3.4.
The temblors sent goods flying off shelves, cracked walls, broke glass and collapsed part of a water flume west of Reno. There were no injuries.
They are mostly shallow, occurring just beneath the surface to within a mile or two.
"Shallow makes us believe this is absolutely not volcanic," Price said.
Mapping of the quakes shows they are clustered around the Mogul and Somersett neighborhoods in northwest Reno, in an area about 2.5 miles long and 1/3 of a mile wide.
Craig dePolo with the Nevada Bureau of Mines and Geology, said he understands the anxiety of residents who have lived with the persistent shaking.
"What's going on is extraordinary," he agreed. "People are being needled by little earthquakes ... for months."
"And the best we can say is we don't know what going to happen."
DePolo, who said he's been through many earthquakes, acknowledged that he, too, is "a little nervous."
The governor and emergency managers urged residents to be prepared by strapping down water heaters or any heavy items that could fall and injure people and to have first aid and food provisions on hand.
Frank Siracusa, head of the Nevada Division of Emergency Management, said state, regional and local agencies train constantly for disasters and have been in daily contact.
"I'd like to say we're prepared, but we can never be too prepared," he said.
The governor said he's "very concerned about the safety of the public," and stressed that residents need to be prepared to minimize risk in the event of a disaster.
Gibbons, himself a geologist, said the earth's movement is what makes the mountains and Nevada landscape so special.
"I find it fascinating about our earth and how it continually evolves over time," he said.
But with Nevada being the second most seismically active state in the continental U.S., he echoed the advice of experts who said large earthquakes are inevitable.
"At some point ... we are going to have a magnitude 6 or 7," Gibbons said.
Earthquake magnitudes are calculated according to ground motion recorded on seismographs. An increase in one full number — from 5.5 to 6.5, for example — means the quake's magnitude is 10 times as great.
A quake with a magnitude of 6 can cause severe damage, while one with a magnitude of 7 can cause widespread, heavy damage.
Copyright © 2008 The Associated Press.
State's buildings prepared for earthquakes
State's buildings prepared for earthquakes
Geoff Dornan
Appeal Capitol Bureau, gdornan@nevadaappeal.com
May 4, 2008, 4:01 AM
Some of the oldest buildings in Northern Nevada and potentially most vulnerable to earthquake damage are owned by the state itself.
The issue was raised because of swarms of small and medium quakes centered in the Verdi area over the past few weeks.
But experts say those century-old masonry buildings - including the Capitol - have been prepared to handle a quake.
During the past 30 years, the Capitol, its octagonal annex, the State Museum, the old Ormsby County Courthouse, the former federal post office and district court - now home to the tourism commission - and the old state printing building have all undergone extensive structural work designed to help them survive a big quake.
The 137-year-old Capitol underwent the most extensive reconstruction.
State Archives Manager Jeff Kintop said that project was made necessary after western Nevada was reclassified into the same earthquake zone as San Francisco.
Three independent engineering firms declared the Capitol "structurally unsound" and "a public safety hazard." In a good quake, they said, the floors could separate from the walls and the stone exterior collapse.
Kintop said that left the state with two options: Tear it down and build a new one or completely reconstruct the historic Capitol.
The 1977 Legislature appropriated $6 million to rebuild. McKenzie Construction of Sparks went to work that year, removing the roof and dome, taking out the floors and the stone interior walls, leaving only the exterior walls.
"It looked like bombed out Dresden," said Kintop.
An extensive system of steel and rebar was installed into the inside of the sandstone blocks that make up the Capitol's exterior. Then concrete was added, new concrete and steel floors were poured and tied into that shell, the lumber roof structure replaced with steel beams and a new, much lighter fiberglass dome put atop the reconstructed Capitol.
In effect, they created a concrete and steel building inside the old sandstone building.
"The inside of the building is being supported by this structure that's independent of the outside walls," said Robbie Oxoby of the Public Works division. "The whole idea is that, even if there is damage to the outside walls, the interior of the building would be OK.
"Basically, the only thing that's original is the exterior."
When they finished the structural work, workmen put the original decorations, marble floors and wainscoting and decorative elements back in their original places, making the interior look like it did when it was new. Even the original staircases, railings and balusters were put back.
But, at the time, lawmakers didn't believe the state could afford to do the same to the 100-year-old annex behind the Capitol. The annex, originally built as the state library at the turn of the century, didn't get the same treatment until 2005.
Central Sierra Construction crews gutted the annex and used the same system of steel reinforcement and sprayed-in concrete to stabilize the exterior walls. Then they rebuilt the interior, trying to keep and restore as much of the original moldings, pillars and other elements as possible. It now houses six modern offices on the main floor with a high-tech media and meeting room upstairs.
Of those original state buildings, only the museum - originally the Carson City Mint - has actually suffered earthquake damage. It was closed to the public after the 1990 earthquake that hit the Bay area caused structural damage that threatened to separate floors and the roof from the sandstone walls. Museum Facility Supervisor Scott Klette said Clark and Sullivan of Reno submitted what state officials said was a very low bid of less than $1 million to do the repairs. He said the company came through, using hundreds of steel braces and straps to stabilize the building by tying walls, floors and roof together.
"It was a life-safety issue, not a preservation issue," said Klette.
He said museum crews had to get into the act as well, disassembling all the exhibits and removing them from the building so workmen could do the job.
"We had to gut the mint," he said.
Just about the only thing that didn't get moved was the historic - and extremely heavy - coin press.
The State Printing Office, completed in 1886, is Nevada's second oldest state building after the Capitol. It got its rebuild when the new state library and archives building was built around it in 1993. Kintop said workmen there didn't want to build a concrete structure inside because the building was so small to begin with. So, he said, they reinforced the walls with steel bars by drilling vertically through them and inserting the steel.
The Ormsby County Courthouse, built in 1922, is one of two structures on the list that, originally, wasn't a state building. But it too is sandstone from the same quarry east of town. Again, Clark and Sullivan of Reno did the work, carefully removing much of the interior with the idea of putting elements including the marble entry walls and floor back in place afterward.
Oxoby said more joists were added to the first floor where the Carson City court clerk's numerous file cabinets had caused it to sag. And again, he said, much of the work involved tying the walls and floors together.
The Laxalt Building, now home to State Tourism, was built by the federal government in 1891 as the post office and district court. It is the only building on the list made of brick instead of sandstone. Oxoby said that building, which was deeded to the state in 1970, was structurally stabilized before it was remodeled into Tourism's new home. He said it has had the necessary improvements made to ensure it won't just collapse in a quake.
Public Works Manager Gus Nuñez said unreinforced masonry buildings are more likely to suffer major damage in a quake than the normal stick-built home.
"Lumber is flexible," he said. "Masonry is rigid."
A wood-framed house will flex in a quake and, although damaged, almost always remain standing. With unreinforced masonry buildings, he said, "you get a good shake, the wall falls down."
The solution, he said, is to tie walls, floors and roof all together. He said the state still has a number of those buildings, but does as much as possible to make them safer with every project. He said on a number of roofing projects at Stewart, for example, the state has taken that opportunity to install braces and ties to better connect the roof to the walls of those buildings.
"The idea is to minimize building damage so people can get out and safely away from the structure," he said. "Anytime we have a building that's unreinforced masonry, that would raise a flag for us."
Asked about the Kinkead Building, now vacant because of concerns it isn't safe, Nuñez said it would take a major quake - and one that actually caused the building to twist, rotate around its concrete core - to collapse the structure. But he said it's a moot point now since the building is vacant and mothballed until the state can fund its demolition.
Appeal Capitol Bureau, gdornan@nevadaappeal.com
May 4, 2008, 4:01 AM
Some of the oldest buildings in Northern Nevada and potentially most vulnerable to earthquake damage are owned by the state itself.
The issue was raised because of swarms of small and medium quakes centered in the Verdi area over the past few weeks.
But experts say those century-old masonry buildings - including the Capitol - have been prepared to handle a quake.
During the past 30 years, the Capitol, its octagonal annex, the State Museum, the old Ormsby County Courthouse, the former federal post office and district court - now home to the tourism commission - and the old state printing building have all undergone extensive structural work designed to help them survive a big quake.
The 137-year-old Capitol underwent the most extensive reconstruction.
State Archives Manager Jeff Kintop said that project was made necessary after western Nevada was reclassified into the same earthquake zone as San Francisco.
Three independent engineering firms declared the Capitol "structurally unsound" and "a public safety hazard." In a good quake, they said, the floors could separate from the walls and the stone exterior collapse.
Kintop said that left the state with two options: Tear it down and build a new one or completely reconstruct the historic Capitol.
The 1977 Legislature appropriated $6 million to rebuild. McKenzie Construction of Sparks went to work that year, removing the roof and dome, taking out the floors and the stone interior walls, leaving only the exterior walls.
"It looked like bombed out Dresden," said Kintop.
An extensive system of steel and rebar was installed into the inside of the sandstone blocks that make up the Capitol's exterior. Then concrete was added, new concrete and steel floors were poured and tied into that shell, the lumber roof structure replaced with steel beams and a new, much lighter fiberglass dome put atop the reconstructed Capitol.
In effect, they created a concrete and steel building inside the old sandstone building.
"The inside of the building is being supported by this structure that's independent of the outside walls," said Robbie Oxoby of the Public Works division. "The whole idea is that, even if there is damage to the outside walls, the interior of the building would be OK.
"Basically, the only thing that's original is the exterior."
When they finished the structural work, workmen put the original decorations, marble floors and wainscoting and decorative elements back in their original places, making the interior look like it did when it was new. Even the original staircases, railings and balusters were put back.
But, at the time, lawmakers didn't believe the state could afford to do the same to the 100-year-old annex behind the Capitol. The annex, originally built as the state library at the turn of the century, didn't get the same treatment until 2005.
Central Sierra Construction crews gutted the annex and used the same system of steel reinforcement and sprayed-in concrete to stabilize the exterior walls. Then they rebuilt the interior, trying to keep and restore as much of the original moldings, pillars and other elements as possible. It now houses six modern offices on the main floor with a high-tech media and meeting room upstairs.
Of those original state buildings, only the museum - originally the Carson City Mint - has actually suffered earthquake damage. It was closed to the public after the 1990 earthquake that hit the Bay area caused structural damage that threatened to separate floors and the roof from the sandstone walls. Museum Facility Supervisor Scott Klette said Clark and Sullivan of Reno submitted what state officials said was a very low bid of less than $1 million to do the repairs. He said the company came through, using hundreds of steel braces and straps to stabilize the building by tying walls, floors and roof together.
"It was a life-safety issue, not a preservation issue," said Klette.
He said museum crews had to get into the act as well, disassembling all the exhibits and removing them from the building so workmen could do the job.
"We had to gut the mint," he said.
Just about the only thing that didn't get moved was the historic - and extremely heavy - coin press.
The State Printing Office, completed in 1886, is Nevada's second oldest state building after the Capitol. It got its rebuild when the new state library and archives building was built around it in 1993. Kintop said workmen there didn't want to build a concrete structure inside because the building was so small to begin with. So, he said, they reinforced the walls with steel bars by drilling vertically through them and inserting the steel.
The Ormsby County Courthouse, built in 1922, is one of two structures on the list that, originally, wasn't a state building. But it too is sandstone from the same quarry east of town. Again, Clark and Sullivan of Reno did the work, carefully removing much of the interior with the idea of putting elements including the marble entry walls and floor back in place afterward.
Oxoby said more joists were added to the first floor where the Carson City court clerk's numerous file cabinets had caused it to sag. And again, he said, much of the work involved tying the walls and floors together.
The Laxalt Building, now home to State Tourism, was built by the federal government in 1891 as the post office and district court. It is the only building on the list made of brick instead of sandstone. Oxoby said that building, which was deeded to the state in 1970, was structurally stabilized before it was remodeled into Tourism's new home. He said it has had the necessary improvements made to ensure it won't just collapse in a quake.
Public Works Manager Gus Nuñez said unreinforced masonry buildings are more likely to suffer major damage in a quake than the normal stick-built home.
"Lumber is flexible," he said. "Masonry is rigid."
A wood-framed house will flex in a quake and, although damaged, almost always remain standing. With unreinforced masonry buildings, he said, "you get a good shake, the wall falls down."
The solution, he said, is to tie walls, floors and roof all together. He said the state still has a number of those buildings, but does as much as possible to make them safer with every project. He said on a number of roofing projects at Stewart, for example, the state has taken that opportunity to install braces and ties to better connect the roof to the walls of those buildings.
"The idea is to minimize building damage so people can get out and safely away from the structure," he said. "Anytime we have a building that's unreinforced masonry, that would raise a flag for us."
Asked about the Kinkead Building, now vacant because of concerns it isn't safe, Nuñez said it would take a major quake - and one that actually caused the building to twist, rotate around its concrete core - to collapse the structure. But he said it's a moot point now since the building is vacant and mothballed until the state can fund its demolition.
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