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-  海外华人地球科学技术协会社区  (http://www.geochina.orghttp://www.geochina.orgindex.asp)
--  site  (http://www.geochina.orghttp://www.geochina.orgbbs.asp?boardid=1)
----  Taiwan seismology and earthquake engineering  (http://www.geochina.orghttp://www.geochina.orgdispbbs.asp?boardid=1&rootid=1&id=10)

--  作者：cpan1
--  发布时间：12/29/2005 3:55:57 PM

--  Taiwan seismology and earthquake engineering
I watched Chinese news on the most recent Taiwan earthquake. It seems to me there is a confusion between magnitude and intensity. At first I thought it was just the media's confusion of scientific and engineering terminology. However, later on I found the so-called expert used the same language. I do not know whether they translated them differently or have their own definition, but at least seismology and earthquake engineering are different fields. What fundamental training in seismology and earthquake engineering they have had?

--  作者：cpan1
--  发布时间：12/29/2005 5:21:45 PM

--  re Taiwan seismology and earthquake engineering
I am in Califnornia. There are so many strong motion seismometers installed around here, almost building-wise. But as far as I can recall, I do not remember I have ever heard from the news that intensity was announced to the public. I had also experienced Hiacheng and Tangshan earthqukes, I never remember intensity had been mentioned to the public. Strong motion seismology is not my field, I should not say much about it. However, to my point of view, intensity is more useful as a reference for earthquake engineering. Even in that case, g is much more useful, because all earthquake designs depend on g, and all seismic risk probablility maps are in g. During an earthquake, everybody is frightened and in panic, so to my point of view, technical announcement should be kept as simple as possible to avoid unnecessary confusion and the risk of unnecessary public panic. I believe that is why they do not announce intensity here and in China.

--  作者：Chien-Hsin Chang
--  发布时间：12/29/2005 5:22:57 PM

--  re Taiwan seismology and earthquake engineering
The Jiji major earthquake was a magnitude 7.3(ML) event. Local magnitude used Richter's scale always. There are different calculated method by magnitude MS (surface wave magnitude) and Mw (Moment magnitude). This event magnitude was 7.6 by Mw scale. The intensity scale is separated to 0~6 seven degrees in Taiwan area. 0 degree : peak ground motion below 0.8 gal(cm/sec/sec) 1 degree : PGA 0.8~2.5 gal 2 degree : PGA 2.5~8.0 gal 3 degree : PGA 8.0~25. gal 4 degree : PGA 25.~80. gal 5 degree : PGA 80.~250.gal 6 degree : PGA more than 250. gal Jiji earthquake has record PGA 980.gal near epicenter( about 10KM ).

--  作者：cpan1
--  发布时间：12/29/2005 5:23:51 PM

--  re Taiwan seismology and earthquake engineering
As to my understanding, a change of widely used scientific terminology is not a simple matter; it must be a necessity. Either it is because new discoveries have made the old terminology to become obsolete such that it can no longer be able to properly represent or describe the named physical phenomenon, or it has been discovered that the old terminology was inadequately defined from the start or simply defined wrong. In either case, you need a special committee to make a wide-scope discussion, as well as a formal presentation such as through publication to tell all the scientists concerned of the reasons why the terminology should be changed. If the feedbacks from the scientists are unanimously in favor, then formally announce the change. However, if there are still controversies, and you still think you are right, you may need a ballot to get an absolute majority. I hope you knew exactly what you were doing and believe you had gone through similar processes at least in Taiwan. However, earthquakes are not a special physical phenomenon occurred and studied only in Taiwan. I am not in a position to solicit opinions from other Chinese-speaking experts outside Taiwan on this change of terminology. However, from Chinese news reports around here I continue to find that, besides the Taiwan news media, nobody has followed your new terminology. Those Chinese-speaking scientists who had talked to the Chinese media around here were still using the old terminology, and even the Chinese newspaper which was already aware of this change still used both ¡°guimu¡± and ¡°jie¡± at the same time for the same earthquake, depending on their news sources. Well, you may say that you do not care about what the others say; what you do care is ¡°Taiwan first.¡± That is fine! Please do not forget seismology is a science and you are supposed doing scientific work; you should exactly know what you were doing. I still remember many years ago, when T. L. Teng was just beginning to introduce seismology to Taiwan, once he said to me, ¡°science has no boundaries.¡± I am not sure what he will say by now. I believe I have already made a mistake; I should not have got involved in such a monkey business after all.

--  作者：cpan1
--  发布时间：12/29/2005 5:24:33 PM

--  re Taiwan seismology and earthquake engineering
In my past comments I used "g" and forgot to define it. "g" is the commonly used unit in earthquake design; 1 g = 980 gal. Therefore, the maximum horizontal acceleration in the Jiji earthquake is 989 gal = 1.009 g, and not 989 g.