When will the Big One Strike SLC?
--updated 7 October 2019--
Almost a month ago [from the original post date of May 24, 2019] , the Church of Jesus Christ of Latter-day Saints announced that the Salt Lake Temple will be closing December 29, 2019 for major structural and seismic renovation. The renovations will be completed sometime in 2024 when there will be a public open house, and then the temple will be rededicated.
https://www.mormonnewsroom.org/article/plans-unveiled-salt-lake-temple-renovation
2024...
If you've read my blog, you've seen that year come up before.
I'm going to guess the Church will want to have the temple rededicated before the April General Conference, which would should be on April 6 and 7 of that year.
Part of the renovations will be adding a seismic base isolation system, and strengthening the walls and towers.
The maximum-strength earthquake expected in the Salt Lake City area is a 7.3. With the isolation system, that temple will only be feeling the equivalent of a 5.1 or 5.2, which should cause much damage at all. Maybe knock a few things over.
https://www.deseretnews.com/article/900066730/heres-how-the-salt-lake-temples-base-isolation-system-will-protect-it-from-earthquakes.html
It's interesting to note the articles I've ready do not give a maximum rating of the base isolation system.
Assuming the system effectively reduces the experienced effects of an earthquake by two full magnitudes, if the area experienced a magnitude 9.5 quake (which seismologists would scoff at and claim as being extremely unlikely) then the temple would experience the effects of a 7.3. From my experience and research, I would guess the temple would survive well enough, especially with the base isolation system, without any major structural damage during such an earthquake.
If I recall right, the temple grounds are also over an area of more solid bedrock, which has a very low likelihood of liquefaction, unlike most of the rest of the Salt Lake valley. Besides being unlikely to experience liquefaction, the solid ground won't amplify seismic waves as much as softer soils.
The following image is the Liquefaction-potential map for Salt Lake City.
The yellow is very low liquefaction potential. There's a dip of yellow from North Temple to about 300 South, and between about 300 West (John Stockton Dr) to State St.
Here's a map I snipped from Google Maps. I've approximated the liquefaction-potential boundary with the red marking, and the Salt Lake Temple has the map marker on it.
The liquefaction-potential map is from 1994, so there may be some more updated information. But, I've also found the geological maps to basically be the same.
So when will a Big One strike Salt Lake City?
My immediate thought when President Nelson announced the upcoming renovations for the Salt Lake Temple during General Conference was that we would likely not have a major earthquake before the temple renovations were complete. That would make 2024 the earliest.
So, we might expect sometime in 2024, probably in the fall (I'd probably put it in November, after the elections), as the time for the first big earthquake.
Would the larger earthquake happen as soon as the next year? Maybe. If it did, it'd probably be spring time.
But, consider this other option. What if a 7.0 earthquake were to strike during the early part of renovations? Maybe within the next two years.
In this scenario, the temple would not be in use. An earthquake of that magnitude would reveal any structural seismic deficiencies that would need to be addressed, which were not previously considered. With that knowledge, the additional issues could be remedied, hopefully without delaying renovations much. Then, after the temple is rededicated it would be sufficiently able to withstand a stronger earthquake, maybe as early as sometime in 2024.
When the temple was being built, the original foundations were made entirely of sandstone. With the threat of a U.S. Army coming, the pioneers buried the foundation. When the threat passed, the foundation was uncovered and cracks were discovered. It was decided that granite would be used instead (at least for the foundation walls down to about 14 feet)
https://www.deseret.com/2018/5/13/20644956/is-the-foundation-of-the-salt-lake-temple-composed-of-granite-or-sandstone#here-is-a-picture-of-construction-which-may-never-be-seen-again-the-sandstone-sub-foundation-to-the-granite-foundations-under-the-main-entrance-to-the-salt-lake-temple-march-30-1963-ralph-t-clark-deseret-news-archives
So, a significant earthquake might reveal factors that were not considered or were overlooked, and allow for immediate changes/modifications to strengthen the structure while it was still being renovated.
In either case, it looks like the really big earthquake is not likely to strike Utah before 2024.
However, a 7.0 earthquake could hit sooner, but if there is nothing that needs to be addressed with the renovations, then we may not see that first quake until 2024.
As a side note. I think the first big earthquake will be around the 7.0 magnitude range. This is what most geologists and seismologists expect. The Wasatch Fault is believed to be capable of producing earthquakes up to the mid or high magnitude-7 range. There will be a much larger earthquake that will happen at a later date, if dreams and visions are to be believed. From the descriptions I've read, this larger quake will likely be in the magnitude 9-range. Scientists, seismologists, geologists and others won't believe you and will tell you the fault isn't capable of producing these mega-thrust level quakes. It could be larger than a 9, but I think the main shock will be in the 9 range and it will cause a multiple fault rupture, meaning other segments of the Wasatch Fault will likely rupture as a result. Multi-fault ruptures end up causing much greater damage than a single fault of the same magnitude.
Almost a month ago [from the original post date of May 24, 2019] , the Church of Jesus Christ of Latter-day Saints announced that the Salt Lake Temple will be closing December 29, 2019 for major structural and seismic renovation. The renovations will be completed sometime in 2024 when there will be a public open house, and then the temple will be rededicated.
https://www.mormonnewsroom.org/article/plans-unveiled-salt-lake-temple-renovation
2024...
If you've read my blog, you've seen that year come up before.
I'm going to guess the Church will want to have the temple rededicated before the April General Conference, which would should be on April 6 and 7 of that year.
Part of the renovations will be adding a seismic base isolation system, and strengthening the walls and towers.
The maximum-strength earthquake expected in the Salt Lake City area is a 7.3. With the isolation system, that temple will only be feeling the equivalent of a 5.1 or 5.2, which should cause much damage at all. Maybe knock a few things over.
https://www.deseretnews.com/article/900066730/heres-how-the-salt-lake-temples-base-isolation-system-will-protect-it-from-earthquakes.html
It's interesting to note the articles I've ready do not give a maximum rating of the base isolation system.
Assuming the system effectively reduces the experienced effects of an earthquake by two full magnitudes, if the area experienced a magnitude 9.5 quake (which seismologists would scoff at and claim as being extremely unlikely) then the temple would experience the effects of a 7.3. From my experience and research, I would guess the temple would survive well enough, especially with the base isolation system, without any major structural damage during such an earthquake.
If I recall right, the temple grounds are also over an area of more solid bedrock, which has a very low likelihood of liquefaction, unlike most of the rest of the Salt Lake valley. Besides being unlikely to experience liquefaction, the solid ground won't amplify seismic waves as much as softer soils.
The following image is the Liquefaction-potential map for Salt Lake City.
(image taken from https://ugspub.nr.utah.gov/publications/public_information/pi-25.pdf)
And here's the zoomed in part where the temple is located
The yellow is very low liquefaction potential. There's a dip of yellow from North Temple to about 300 South, and between about 300 West (John Stockton Dr) to State St.
Here's a map I snipped from Google Maps. I've approximated the liquefaction-potential boundary with the red marking, and the Salt Lake Temple has the map marker on it.
The liquefaction-potential map is from 1994, so there may be some more updated information. But, I've also found the geological maps to basically be the same.
So when will a Big One strike Salt Lake City?
My immediate thought when President Nelson announced the upcoming renovations for the Salt Lake Temple during General Conference was that we would likely not have a major earthquake before the temple renovations were complete. That would make 2024 the earliest.
So, we might expect sometime in 2024, probably in the fall (I'd probably put it in November, after the elections), as the time for the first big earthquake.
Would the larger earthquake happen as soon as the next year? Maybe. If it did, it'd probably be spring time.
But, consider this other option. What if a 7.0 earthquake were to strike during the early part of renovations? Maybe within the next two years.
In this scenario, the temple would not be in use. An earthquake of that magnitude would reveal any structural seismic deficiencies that would need to be addressed, which were not previously considered. With that knowledge, the additional issues could be remedied, hopefully without delaying renovations much. Then, after the temple is rededicated it would be sufficiently able to withstand a stronger earthquake, maybe as early as sometime in 2024.
When the temple was being built, the original foundations were made entirely of sandstone. With the threat of a U.S. Army coming, the pioneers buried the foundation. When the threat passed, the foundation was uncovered and cracks were discovered. It was decided that granite would be used instead (at least for the foundation walls down to about 14 feet)
https://www.deseret.com/2018/5/13/20644956/is-the-foundation-of-the-salt-lake-temple-composed-of-granite-or-sandstone#here-is-a-picture-of-construction-which-may-never-be-seen-again-the-sandstone-sub-foundation-to-the-granite-foundations-under-the-main-entrance-to-the-salt-lake-temple-march-30-1963-ralph-t-clark-deseret-news-archives
So, a significant earthquake might reveal factors that were not considered or were overlooked, and allow for immediate changes/modifications to strengthen the structure while it was still being renovated.
In either case, it looks like the really big earthquake is not likely to strike Utah before 2024.
However, a 7.0 earthquake could hit sooner, but if there is nothing that needs to be addressed with the renovations, then we may not see that first quake until 2024.
As a side note. I think the first big earthquake will be around the 7.0 magnitude range. This is what most geologists and seismologists expect. The Wasatch Fault is believed to be capable of producing earthquakes up to the mid or high magnitude-7 range. There will be a much larger earthquake that will happen at a later date, if dreams and visions are to be believed. From the descriptions I've read, this larger quake will likely be in the magnitude 9-range. Scientists, seismologists, geologists and others won't believe you and will tell you the fault isn't capable of producing these mega-thrust level quakes. It could be larger than a 9, but I think the main shock will be in the 9 range and it will cause a multiple fault rupture, meaning other segments of the Wasatch Fault will likely rupture as a result. Multi-fault ruptures end up causing much greater damage than a single fault of the same magnitude.
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