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FW: Mistreatment of Seismology Issues[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaoc <seaint(--nospam--at)seaint.org>
- Subject: FW: Mistreatment of Seismology Issues
- From: "La Count, Curt" <Curt.LaCount(--nospam--at)Jacobs.com>
- Date: Wed, 21 Oct 1998 11:34:00 -0700
As far as the public is concerned (and those people who insure the public), it would be more usefull to talk about probabilites and performance categories, unless you want to warrant, with your stamp, that a given design will withstand an earthquake of a given Richter magnitude with repairable damage (lawyer definition, not yours). I don't care how easy the calculation is, I wouldn't touch it with a ten foot pole. Curt La Count ---------- From: Yank2002(--nospam--at)aol.com To: seaint(--nospam--at)seaint.org Subject: Mistreatment of Seismology Issues Date: Wednesday, October 21, 1998 8:31AM On October 13, 1998 I sent the following question addressed to California Department of Conservation, Seismology Division: How do you define "acceptable level of seismic hazard" in terms of Richter scale magnitude? Thank you ... The following response was received: > From: Reichle, Michael > Sent: Monday, October 19, 1998 10:01 AM > To: 'Yank2002(--nospam--at)aol.com' > Cc: Beeby, Dave > Subject: RE: Acceptable levels of seismic hazard > > There is no "acceptable level of seismic hazard," because we have no > control over the shaking. We generally use the term "acceptable level of > risk," which refers to how buildings and other structures respond to the > shaking. What the "acceptable level" actually is depends on your > structure. For example, buildings built according to the Uniform Building > Code are built to life safety standards. They should not collapse, but > could be severely damaged. Schools and hospitals in California are built > to remain operational following an earthquake. > > Future building codes will incorporate "performance-based design" that > will permit the owner to determine the performance level (or risk level) > above the life safety standard that he may wish for his building. The > Federal Emergency Management Agency has some publications on > performance-based design, if you wish to pursue that subject further. > > I hope this information is helpful. Feel free to let me know if you have > any further questions. > > Michael Reichle > Supervising Geologist On October 20, 1998 I sent the following E-Mail message to Michael Reichle: Subj: Re: Acceptable levels of seismic hazard Date: 98-10-20 16:00:20 EDT From: Yank2002 To: mreichle(--nospam--at)consrv.ca.gov Thank you for your response. I am / was a practicing structural engineer in the State of California for the past 30 years. I think I know that due to a variety of reasons structures designed "to code" do not always behave as they are "officially" expected to behave. (1971 Sylmar/San Fernando hospital collapse; 1994 California State University Northridge structures collapses; 1994 near collapse of MAJOR highrise structures in downtown Los Angeles - about which, not surprisingly, mostly California structural engineers are aware of; the public was and still is kept in the dark about this super-major seismic disaster that almost materialized and almost destroyed a good part of downtown Los Angeles). The so-called "life safety standards" you mentioned in your E-Mail, defined by the state (and federal) people are misleading as they inform the public that certain special structures (hospitals and schools) are life-safe. In case of school structures the "life safety standards" statement misinforms the parents by suggesting that they should not worry about their children's safety while they are in school. The reality, however, was and is different. It is easy to mathematically translate Zone 4 seismic code requirements into the equivalent of Richter scale magnitude. From what I have discovered, this unofficial but reasonable (I think) translation indicates that Seismic Zone 4 design requirements equal about 6.5 magnitude on the Richter scale under "average" geological soil conditions. The magnitude of both earthquakes, Sylmar and Northridge, exceeded 6.5 and only due to the timing of both quakes (early morning hours) the damage to affected communities was 50+ deaths for each event in addition to physical damage to many structures ($20 billion+ for the 1994 event). An earthquake of 6.5 magnitude taking place during "business hours" would increase death toll by the factor of at least 10. Both earthquakes (Sylmar and Northridge) were seismic energy releases of minor faults. The release of seismic energy by a major fault, the San Andreas, in a close vicinity of Los Angeles (Pasadena, Glendale, etc.) or San Francisco, would cause much more physical damage to structures and the death toll would probably run into thousands. Since Los Angeles and San Francisco are the two major targets of San Andreas seismic energy release of more than 7.3 magnitude as projected by Caltech, U of California at Berkeley and Stanford U theories (which can be proven by mathematically based translation), the "acceptable level of risk" has no practical meaning to anyone other than to the self- serving state officials formulating such incomprehensible definitions. If the owner of a property (residential, commercial, or whatever) approaches the structural engineer and asks him a question: Will my structure be able to withstand the earthquake of magnitude of (say) 6.8? The structural engineer is not able to answer the question because he was not given the tools to translate the 6.8 Richter scale magnitude earthquake into "how the structure should be built and how the connection details must be developed to withstand such an earthquake". The only statement he can make is that the structure seismically conforms (or does not conform) to the latest building code. Since the "acceptable level of risk" statement does not mean anything in terms of Richter magnitude numbers, the owner of the structure is at a loss what to do next if he wants the structure to withstand a 6.8 (or any other ) magnitude earthquake. The structural engineer wouldn't be of any help as he also doesn't know what has to be done to the structure (existing or new) so it withstands the earthquake of this particular (or any other) magnitude. Since general public knows very well what kind of damage can be expected when (say) 6.4 earthquake strikes but has absolutely no idea as to what kind of damage can result when "life-safety standard"-compliant structure is hit by the same magnitude earthquake, I think the process of identifying seismic forces acting in seismic regions of California should be convertible to Richter scale magnitude (or any other meaningful scale system). The number designated earthquake is understood by most humans living on this planet; "the life-safety standard"-compliant structure designation is good only for the technically-inclined poets. As it turns out the-so-called "life-safety standards" did not work very well for school structures in Northridge nor for hospital facilities in Sylmar. As a result of all of it: If an individual officially or unofficially inquires geologists or structural engineers about the state of seismic affairs in California, he will be not necessarily deliberately but certainly knowingly misinformed and his question will never be truthfully answered only because the "acceptable level of risk" is a meaningless concept. Your comments would be appreciated. (*) Pasadena is only 33 miles away perpendicularly from the point on the San Andreas fault (the shortest distance) where seismologists expect the major (7.0+) seismic release of energy to happen. The latest changes of the seismic code requirements DO NOT consider special "short distance" effects of a major earthquake event generated by the San Andreas. The end of my message. Before I receive the response from the Conservation people, I would like to put the issue on the conference table of structural engineers for possible discussion. I realize that "structural engineering officialdom" would want to shoot me in the back ... but they don't know where I live. So, for the time being I am safe. By the way ... I don't smoke pot, don't use hallucinatory drugs nor drink alcohol. Thank you for your time.
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