Anyone remember the Missouri earthquake? It was an area no one believed was at risk.

Salt Lake is full of houses that are poor in an earthquake, a 9th mag earthquake would ruin Salt Lake City. BTW, did a little digging about tsunamis, seems the worse scenario is a steep shore line. This concentrates the kinetic energy on the shoreline. The initial event determines the energy contained in the waves. Incidentally, I am currently working on a rehabilitation, including a

seismic upgrade, on a stone and adobe house in Ephraim. The Japan quake has me thinking more about these issues even more than usual. If you live in an unreinforced masonry home, make sure your will is in order.

Kim

-----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Rodger C. Fry Sent: Friday, March 18, 2011 2:01 PM To: utah-astronomy@mailman.xmission.com Subject: [Utah-astronomy] Japan Earthquake Discussion

This is mildly off topic but does talk about crustal tides and earthquake predictions.

I don't know much about this guy but what he is saying may provide for an interesting discussion.

Time will Tell.

Follow this link:

http://www.youtube.com/watch?v=xQXDt4VdS0E

Rodger Fry

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Yes, amplitude increases as water depth deceases and you are right bays can contribute to that. I suspect some of problem with these shores is the corresponding land is near sea level so it does not take a huge wave to translate into reaching a long way in shore. This was the case in Thailand. Atolls I suspect are small enough that they have little effect, not big enough land mass to concentrate the energy. There are many things contributing to height, exposure is one, it seemed Hawaii gave a small profile to this one, perhaps if it hit Hawaii broadside the damage and surge would have been greater.

There is energy loss from friction as the sea depth decreases, the case I refer to is a wave approaching a large land mass. If there is steep run up little of the waves energy would be released until it meets land causing the waves to break closer to shore, so more energy is released at the shore. I believe this is only the case from earthquakes IE the event happens on the sea floor. The sea depth decrease when approaching all land masses, with steeper approach the energy gets concentrated closer to shore. A tsunami caused by a meteor impact would be different. I remember reading that meteor impacts have created waves that have washed over much of N America, it would make no difference what your coastlines topography is. A dangerous undersea topography for a tsunami is a seafloor that becomes

shallower and shallower, as it allows the waves to build up dramatically -- see the illustration here: http://www.pmel.noaa.gov/pubs/outstand/gonz2088/images/image4.jpg . With an island atop a steep abutment, as with some Pacific atolls, the wave can just pass through, causing no harm. If that weren't the case I would have died in 1964. And the same island, Kwajalein, got through the recent tsunami without damage. Recently I heard that tsunami comes from the word for "harbor wave," because harbors are likely to have shallowing bottoms and a bowl-like structure that funnel the power of the tsunami in. But I have suspect that when one hits a really wide shore it causes damage regardless of the ocean bottom. Thanks, Joe

--- On Fri, 3/18/11, erikhansen@thebluezone.net <erikhansen@thebluezone.net> wrote:

...

From: erikhansen@thebluezone.net <erikhansen@thebluezone.net> Subject: Re: [Utah-astronomy] Japan Earthquake Discussion To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Date: Friday, March 18, 2011, 3:38 PM

...

Anyone remember the Missouri earthquake? It was an area no one believed was at risk.

Salt Lake is full of houses that are poor in an earthquake, a 9th mag earthquake would ruin Salt Lake City.

BTW, did a little digging about tsunamis, seems the worse scenario is a steep shore line. This concentrates the kinetic energy on the shoreline. The initial event determines the energy contained in the waves.

Incidentally, I am currently working on a rehabilitation, including a

...

seismic upgrade, on a stone and adobe house in Ephraim. The Japan quake has me thinking more about these issues even more than usual. If you live in an unreinforced masonry home, make sure your will is in order.

Kim

-----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Rodger C. Fry Sent: Friday, March 18, 2011 2:01 PM To: utah-astronomy@mailman.xmission.com Subject: [Utah-astronomy] Japan Earthquake Discussion

This is mildly off topic but does talk about crustal tides and earthquake predictions.

I don't know much about this guy but what he is saying may provide for an interesting discussion.

Time will Tell.

Follow this link:

http://www.youtube.com/watch?v=xQXDt4VdS0E

Rodger Fry

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Kim, it's been a long time since I was in the pre-architecture program at the U, but I seem to recall that in addition to failed structures themselves, much of the damage here would be the result of all the construction built on ancient sand and gravel bars surrounding the valleys. I recall one professor who claimed that most of the bench structures will simply slide-off the side of the mountain when the "big one" hits and all that clay, sand, and buried talus turns to jello. All those million-dollar houses will become buried in a pile of rubble at the bottom of the benches. Can you comment on that, as a professional architect? On 3/18/11, Kim Hyatt <kimharch@cut.net> wrote:

Incidentally, I am currently working on a rehabilitation, including a seismic upgrade, on a stone and adobe house in Ephraim. The Japan quake has me thinking more about these issues even more than usual. If you live in an unreinforced masonry home, make sure your will is in order.

Chuck, I've been on the road and just arrived home, so I'm only now getting to today's emails. Just so you know I wasn't ignoring you... Much of the ancient lake bed from Lake Bonneville is prone to "soil liquefaction," which I think is the first risk to which you refer. If wet enough, loose soils, primarily sandy soils may lose strength and essentially become a viscous liquid during ground shaking. Here's a link to a short discussion and a liquefaction potential map for most of the Salt Lake area: http://geology.utah.gov/online/pdf/pi-25.pdf. During an earthquake, the most likely mechanism for the failure of soils on mountainous slopes is not necessarily the same as soil liquefaction, although saturated soils are still more likely to fail. Most of the risk of homes sliding off the mountains that your professor described is not due to anything special about the Salt Lake area. Obviously, the very nature of mountains (sloping surfaces, unconsolidated slopes, etc.) increases the potential for soil failures, especially when the earth shakes. That view comes with a very high risk, as folks in southern California and other areas keep experiencing, with or without an earthquake. One other possibility (Rodger may know more about this) is that numerous developments in the foothills of the Wasatch Mountains have been or are being built right on top of some of the minor faults that are part of the Wasatch Fault system. Fault escarpments as high as 30 feet and only a few hundred years old have now become landscape features in "exclusive" neighborhoods. (I'll have to do some digging to find photos.) I don't think that there are many planning/zoning controls in place in Utah to prevent people from being so foolish. So, for what it's worth, there's my professional lesson for the day. (Invoice to follow.) Kim -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Tuesday, March 22, 2011 2:26 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Japan Earthquake Discussion Kim, it's been a long time since I was in the pre-architecture program at the U, but I seem to recall that in addition to failed structures themselves, much of the damage here would be the result of all the construction built on ancient sand and gravel bars surrounding the valleys. I recall one professor who claimed that most of the bench structures will simply slide-off the side of the mountain when the "big one" hits and all that clay, sand, and buried talus turns to jello. All those million-dollar houses will become buried in a pile of rubble at the bottom of the benches. Can you comment on that, as a professional architect?

Joe, this isn't anything about which I have specific information. I assume that a fault doesn't actually "migrate" but that seismic activity may cluster in a given area at one time and later cluster somewhere else. So, the activity might migrate, but not the fault. If this is true, I think the implication is that a period of relative quiet could also mean that stresses would be building where there is less activity. I've long understood that continued low-level movement is a good thing, as opposed to sudden jolts after long periods of quiet, a la Japan and Indonesia. I'm unfamiliar with the data, but I think that the Wasatch Fault has been pretty quiet for a long time. Again, I'm guessing that Rodger would know a good deal more about this stuff. Kim -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Joe Bauman Sent: Wednesday, March 23, 2011 12:33 AM To: Utah Astronomy Subject: Re: [Utah-astronomy] Japan Earthquake Discussion I have heard that the active faults have migrated to the west, a bit away from Salt Lake City's slopes and more toward the Great Salt Lake region. Anything to this, fellows? --- On Tue, 3/22/11, Kim Hyatt <kimharch@cut.net> wrote:

From: Kim Hyatt <kimharch@cut.net> Subject: Re: [Utah-astronomy] Japan Earthquake Discussion To: "'Utah Astronomy'" <utah-astronomy@mailman.xmission.com> Date: Tuesday, March 22, 2011, 11:40 PM Chuck, I've been on the road and just arrived home, so I'm only now getting to today's emails. Just so you know I wasn't ignoring you...

Much of the ancient lake bed from Lake Bonneville is prone to "soil liquefaction," which I think is the first risk to which you refer. If wet enough, loose soils, primarily sandy soils may lose strength and essentially become a viscous liquid during ground shaking. Here's a link to a short discussion and a liquefaction potential map for most of the Salt Lake area: http://geology.utah.gov/online/pdf/pi-25.pdf.

During an earthquake, the most likely mechanism for the failure of soils on mountainous slopes is not necessarily the same as soil liquefaction, although saturated soils are still more likely to fail. Most of the risk of homes sliding off the mountains that your professor described is not due to anything special about the Salt Lake area. Obviously, the very nature of mountains (sloping surfaces, unconsolidated slopes, etc.) increases the potential for soil failures, especially when the earth shakes. That view comes with a very high risk, as folks in southern California and other areas keep experiencing, with or without an earthquake.

One other possibility (Rodger may know more about this) is that numerous developments in the foothills of the Wasatch Mountains have been or are being built right on top of some of the minor faults that are part of the Wasatch Fault system. Fault escarpments as high as 30 feet and only a few hundred years old have now become landscape features in "exclusive" neighborhoods. (I'll have to do some digging to find photos.) I don't think that there are many planning/zoning controls in place in Utah to prevent people from being so foolish.

So, for what it's worth, there's my professional lesson for the day.

(Invoice to follow.)

Kim

-----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Tuesday, March 22, 2011 2:26 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Japan Earthquake Discussion

Kim, it's been a long time since I was in the pre-architecture program at the U, but I seem to recall that in addition to failed structures themselves, much of the damage here would be the result of all the construction built on ancient sand and gravel bars surrounding the valleys.  I recall one professor who claimed that most of the bench structures will simply slide-off the side of the mountain when the "big one" hits and all that clay, sand, and buried talus turns to jello.  All those million-dollar houses will become buried in a pile of rubble at the bottom of the benches.

Can you comment on that, as a professional architect?

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As y'all may know, the Richter Scale (and similar Moment Magnitude scale) is simply a measure of the total energy output of an earthquake. Structures are not designed for a given magnitude quake but are designed based on a theoretical ground acceleration caused by earth shaking. Every large earthquake will cause codes to be re-written, but they seem to be coming much faster now than a few decades ago, and even faster than new data can be incorporated into building codes. Check out this page: http://www.infoplease.com/ipa/A0001439.html. Notice the number of significant events in recent years. Frequency of events appears to be increasing, but I don't know enough about the data or statistics to know if it is actual or merely perceived. Kim -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of erikhansen@thebluezone.net Sent: Friday, March 18, 2011 4:19 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Japan Earthquake Discussion

The most telling comparison I saw was damage done in S. California from a 7th or 8th mag quake that lasted for seconds. Interstate Bridges collapsed along with other extensive damage in an area "prepared" for quakes. The shaking in Japan lasted several minutes, this type of quake would devastate S. California, or any urban area for that matter. They also mentioned that the Nuclear Power plants were not designed to withstand an earthquake of this magnitude. How confident are you that S California N Plants are built to withstand any magnitude of earthquake that is possible? The one proposed for Green River? Cost evidently trumps safety.

This is mildly off topic but does talk about crustal tides and earthquake

predictions.

I don't know much about this guy but what he is saying may provide for an interesting discussion.

Time will Tell.

Follow this link:

http://www.youtube.com/watch?v=xQXDt4VdS0E

Rodger Fry

_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com

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