Editor's note: New estimates for what a 7.0 earthquake could do to the
Wasatch Front are scary: It could kill more than 6,000 people, injure 90,000
and cause a $40 billion economic hit. In a five-part series, the Deseret
Morning News describes such a future quake as if worst-case scenariosproved to be true.
It is 2 p.m. on Feb. 1, 2008, a freezing, snowy Friday. Most people are still at work or school which, unfortunately, is the worst-case scenario for what is about to happen.
The next few seconds will release geologic pressure that built over 13 centuries, and as scientists had predicted back in 2006 will soon kill 6,200 Utahns, injure 90,000 more, at least moderately damage 42 percent of all local buildings and cause $40 billion in economic losses.
What will long be called the great Utah earthquake of 2008 is hitting the Wasatch fault near Salt Lake City and will measure 7.0 on the Richter scale a bit smaller than the 7.1 Loma Prieta earthquake near San Francisco in 1989, or the 7.5 that hit Lake Hebgen, Mont., near Yellowstone in 1959.
The coming damage will closely match worst-case predictions made in 2006 (with the aid of a Federal Emergency Management Agency computer program) by Bob Carey, the earthquake director for the state's Office of Emergency Services.
Of course, 2006 was also when Carey and numerous other officials warned that government could not handle such a catastrophe and said that personal and family preparedness would be the key to how people fare.
Utahns now will find they will need to depend on such preparation for far longer than officials in previous decades had once warned and may need to survive with their "72-hour" emergency kits for five days or longer.Police, fire and other emergency responders will be too busy to reach most people for days so individuals and families will have to rely on themselves and their neighbors for help.
Warnings were correct
Local geologists warned as early as the 1880s that a big earthquake striking the Wasatch Front was not a matter of "if" but "when."
After all, about 700 earthquakes hit Utah every year including about 13 that are magnitude 3.0 or larger and are felt by residents. University of Utah geologists had said recently that the chance of a large earthquake on the Wasatch Front during the next 50 years is about one in five.
Geologists for years watched stress build along the Wasatch Fault as its adjacent sides one at the base of the mountain range, the other the beginning of the valley stretched apart in reaction to earlier, prehistoric compression. For example, recent scientific measurements showed the "valley side" of the fault being stretched to the west by about 2 millimeters a year, or 0.8 inches a decade.
University of Utah seismologist Robert Smith describes such fault stress as being "slowly loaded like a stretched rubber band that suddenly breaks when its strength is exceeded."
Also, earthquakes of about magnitude 7.0 occur on average every 200 to 300 years somewhere on the broad Wasatch Front area, according to Walter Arabasz, director of the University of Utah Seismograph Stations.
He also said they occur on average about once every 1,300 years on the Salt Lake City segment of the Wasatch fault.
When did that last happen? "About 1,300 years ago," Arabasz said back in 2006.But such quakes are not uniformly spaced and could occur any time enough pressure has built.
The fault ruptures, releasing 1,300 years of built-up pressure, about 10 miles deep. Arabasz said that is typical for a 7.0 quake. This quake begins far beneath a point about the middle of the Salt Lake Valley. It is a worst-case scenario site at the middle of the Wasatch Front, so the quake within seconds is felt along all the urban area there.
The fault slippage rips upward at a 60-degree angle toward the surface at six times the speed of sound, reaching the surface in two seconds. On the surface, the ground on the "mountain side" of the fault line is suddenly shoved upward, while the "valley side" slips downward.
The movement soon leaves a new 10-foot-tall ledge or "scarp" a height that varies at different points along the fault as scientists had predicted. The scarp is 29 miles long and now divides areas west and east of it like a great wall. Roads that were once level now have a 10-foot drop-off. Power, water and gas lines there snap.
Some expensive homes had been built atop the old fault scarp left by ancient earthquakes which is now suddenly 10 feet higher in spots. The view of the valley from such points just above the old scarp cliffs had been spectacular.
Smith, in fact, had observed jokingly during a 2006 presentation, when he showed photos of such precariously perched homes, that, "Fault scarp provides wonderful homesites." Some of those homesites are now newly vacant, except for rubble.
Such earth breakage and scarp formation is occurring all along the main branches of the Salt Lake City segment of the Wasatch fault one of 10 independent segments of the larger fault. This segment runs from Corner Canyon in Draper along the base of the Wasatch Mountains to about 4500 South.
At that point, the fault's most active branch moves to a spot out in the valley floor, near Cottonwood Mall. It runs northward roughly along 1300 East to about 100 South in downtown Salt Lake City, then east to University Hospital. Branches also run along the side of Ensign Peak, and between East High School and University Hospital.
Damage and scarp formation is also occurring along two west valley faults, which geologists say tend to shake "in sympathy" when the larger Wasatch fault moves.
The Taylorsville Fault roughly follows I-215 northward from about 4700 South to Rose Park. The Granger Fault runs diagonally northwest from a point about 2700 West and 5400 South to about North Temple and 5600 West.
A scarp about 3 feet high forms along parts of those west valley faults (with the higher "mountain side" on the west instead of the east), as scientists earlier predicted.That 3-foot scarp is not as high as the scarp along the main branches of the Wasatch fault, but the movement is enough to snap transportation and utility lines, divide communities and cause significant damage.
A huge area shakes
Damage is not limited to Salt Lake County. The entire Wasatch Front is now shaking from Brigham City on the north to Santaquin on the south, and from Tooele on the west to Coalville on the east.
It is affecting 80 percent of the population of Utah.
Shaking is so severe throughout Salt Lake County that virtually no one there is able to stand without falling. Unsecured hot-water heaters in many homes shake loose and break natural gas and water lines. Fires start.
Bookcases, furniture, pictures and other debris fall on people inside homes. Some who try to run outside are killed or injured by falling objects. (In contrast, the high and heavily loaded shelves in Lowes and Home Depot hardware stores do not fall because owners, working with the state, decided to anchor shelves for quakes.)
Collapsing buildings and walls are also killing and injuring people throughout the quake area especially in older "unreinforced masonry" buildings made of bricks and mortar without reinforcing steel.
Next, the severe shaking makes some saturated, sandy soils act like a liquid, or more accurately like quicksand. This "liquefaction" causes some buildings to sink or roll over in unstable soils. Landslides follow in some areas.
Significant liquefaction occurs along the Jordan River. Most bridges across the river fail as was predicted by state emergency officials in 2006 for such a quake. This essentially cuts the valley in half again, hampering emergency transportation and limiting how much each half will be able to help the other.
Actually, Salt Lake County is now essentially divided into six parts a worst-case scenario that Carey said in 2006 was possible and crossing between them will not be easy for emergency responders and others.
The sections include the area east of the new, higher Wasatch fault scarp; west of there to the Jordan River; west of the river to the new Taylorsville fault scarp; between it and the new Granger Fault scarp; and the area west of that to the Oquirrh Mountains.
Also, Salt Lake and Davis counties are essentially cut off from each other because of failure of some older freeway bridges which the state had planned to replace soon and damage and fires at oil refineries at the border of the two counties.
All this damage has happened in under a minute.
People near the Wasatch fault itself felt the worst of the shaking for only 10 to 15 seconds. Utah Geological Survey maps in 2002 said the most severe of all shaking would be in those areas near the main fault.
But deep, loose sedimentary soils on the "valley side" of the fault actually amplified ground shaking in some areas, and made residents there feel it longer about 20 to 30 seconds, with some reverberations felt for up to 50 seconds after the rupture.
Robert Archuletta, a seismology professor at the University of California at Santa Barbara, was one who predicted in 2006 that the overall worst ground shaking would happen in areas over such deep soil on the valley floor where a huge segment of the Salt Lake Valley population lives."The strongest shaking will be about 1 to 4 kilometers (up to about 2.5 miles) from the (Wasatch) fault . . . , roughly to about where I-15 is," Archuletta said in a 2006 presentation. "As a consequence, the ground motion is strongest where the people are."
A damage snapshot
A quick snapshot shows some of the monumental destruction that faces the area, or soon will. The extensive damage is hit-and-miss like the impact of a tornado hitting one house and missing a neighboring one because of differences in soil and geology in different areas, and also in construction methods used.
But about 6,200 people are dead. Carey, with state emergency services, said in 2006 that such a quake could kill between 2,200 and 6,200 and the worst-case has occurred.
Sadly, more than 700 students and teachers were killed at schools, and 13,000 more were injured there.
More than 90,000 people total are injured in the quake area.
Of them, about 66,300 suffer only minor "bandage" type injuries. Another 20,500 suffer injuries that will require hospitalization, but the injuries are not considered life-threatening, such as broken bones. Another 3,200 have major injuries that will be life-threatening if not treated quickly.
Unfortunately, hospitals have taken a major hit. Of 38 hospitals in the Wasatch Front quake area, 15 have suffered at least moderate damage and four are considered damaged beyond repair as was predicted by computer modeling in 2006 (but which had been questioned at the time as probably more severe than was truly likely).
About 240,000 buildings of all types are at least moderately damaged. That's 42 percent of the buildings in the quake area.
About 120,000 of them are considered damaged beyond repair, including 99,000 single-family homes; 14,000 other residential buildings, such as apartments; 4,500 commercial buildings; 160 government buildings; 79 churches; and 1,600 industrial buildings.
Significantly, as people start looking for help, about a quarter of all area police and fire stations have themselves suffered at least moderate damage and a handful are beyond repair. One emergency communications center in Salt Lake City has been knocked out of service.
About 152,000 people are now newly homeless, and it is a freezing winter day.
Of 2,270 highway bridges in the quake area, 469 have at least moderate damage and 140 are considered beyond repair. Of 33 railway bridges, three have moderate damage. That, plus the winter storm, will slow the delivery of emergency help.
About 35 million tons of debris has been generated, as predicted by computer modeling in 2006. It will require 1.4 million truckloads to remove.
More than 286,000 homes are now without water service, and more than 240,000 are without electricity. Damage to gas and telephone lines is extensive. Most cell phone communications have been knocked out.
About 70 fires are burning, mostly ignited by broken natural gas pipes. The fires alone soon will displace about 4,700 people and burn about $208 million worth of structures, as Carey had predicted in 2006 with computer modeling.Also, because the quake struck during the workday, many people are separated from their at-home first-aid and 72-hour emergency kits. Few followed state suggestions to have some such supplies in their cars or at work.
As bad as the damage is, it could have been even worse. For example, if the the earthquake had been a bit more powerful, it could have tilted the valley floor enough to make the Great Salt Lake or Utah Lake permanently flood many populated areas including parts of downtown Salt Lake City.
Smith, who co-wrote a study looking at that possibility, said in 2006 that a 7.3 on the Wasatch fault could lead to valley tilting that would permanently flood areas along the eastern shore of the Great Salt Lake. He said then that he thought a 7.0 would be too small to do that, but he had not done computer modeling on it.
He added that a 7.5 is considered to be the maximum credible size for an earthquake along the Wasatch fault.
Areas that would have been flooded include Salt Lake City International Airport, and much of that city west of I-15 and roughly north of I-80 plus some downtown areas. Much of Davis County could also have been affected, including areas in Centerville and Farmington west of I-15.Also, major dams above Salt Lake City, Ogden and Provo survived the 2008 quake. But had it hit 20 years earlier before major seismic upgrades to dams officials said structures such as Mountain Dell, Pineview and Deer Creek dams likely would have failed, causing devastating flooding below, on top of other destruction by the quake.
Carey said in 2006, as he predicted the damage from such an earthquake, "It would be a catastrophic event. It will go well beyond our ability to take care of it."
Now, amid the overwhelming damage and casualties, relatively few police and fire officials are on duty to try to handle it if they can get across collapsed bridges, quake scarps and through debris to reach those in need, and if their sometimes-old police and fire stations did not collapse and trap equipment (as some did).
"When you look at someplace like Sandy, and it has 80,000 people and they have (only a few dozen) firemen or so on duty, it's very limited what they will be able to do," Carey said back in 2006.
Also, emergency planners long figured that even among those few on-duty firefighters and police who are available, many would go home to check on their own families making emergency response even more short-handed.
"Hurricane Katrina showed that many police and first responders may go home to take care of their families," Brian Garrett, director of the state Office of Emergency Services, said in 2006. It happens again after this earthquake.
Carey predicted in 2006, again correctly, that first responders would rely on emergency training to do a quick triage on disasters facing them. They give priority to "hospitals, nursing homes and maybe elementary schools" that sustained severe damage or collapse where many who cannot help themselves are in dire danger.
"Fires are probably at the bottom of their list for things to worry about," Carey had predicted. So many of the fires started by the earthquake burn uncontrolled. First responders are also too overwhelmed to immediately help most people trapped or hurt in individual homes so such victims must depend on their families and neighbors.
Initial response is further hampered because Salt Lake City's emergency dispatch center has been knocked out of service because of damage to the city Public Safety Building at 315 E. 200 South, a nearly 50-year-old office tower built before seismic safety steps were well-known or required.
The city's police and fire chiefs warned in 2006 that the building was not safe in an earthquake. They sought $108.2 million for a new building, part of a proposed $150 million bond that would have also improved many other police and fire stations.
But the cost was high, and opposition blocked it late in 2006 and 2007.
When the bond was first proposed in March 2006, Mike Stever, the city's emergency management director, said, "It is of paramount importance to have a public safety building that is earthquake sound. Our dispatch is in that (old) building, and it would not take an earthquake as big as a 7.0 to cause problems."
He noted that even if the dispatch center there survived a quake, the many windows on that building would be knocked out and if it happened on a wintry day, such as the day of the 2008 quake, the storm would quickly come indoors into what was left of the dispatch center, harming equipment and closing it.
As Stever had predicted, that dispatch center closure forces the Valley Emergency Communications Center which handles 911 calls for other agencies in the valley to also handle calls from Salt Lake City, and to handle dispatch for it. But that center is already overwhelmed, trying to handle problems in other parts of the county.
Stever had warned earlier, "I think people in our valley have expected to call 911 and have help there in three minutes. But in the event of a catastrophic event, it's not going to happen. People are going to be on their own. It will give new meaning to individual and family preparation."
Garrett, director of the state Office of Emergency Services, said in 2006 that may be the central lesson of all the computer modeling and emergency exercises agencies conducted through the years about how to handle catastrophes.29 comments on this story
He said accurately in 2006, "The impact to the community is going to be huge. And it is going to be imperative for our recovery for an event of this magnitude that our citizens are prepared. The citizens most prepared are the ones who are going to fare better."
Carey added at the time, "The bigger the earthquake is, the tougher it will be for the government to take care of you."As arranged well in advance, other counties, states and federal agencies will begin almost immediately shipping resources and people to help. But it will take time, especially with winter storms and the extensive damage.
Monday: How structures from homes to schools, churches and bridges fare in the great earthquake of 2008.