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大地震：預(yù)報 pk 預(yù)測 (中文版 ) 作者：直言了 四川5/12大地震爆發(fā)后，中國和世界上的許多人提出了一個大問題：能否預(yù)測地震？ 閱讀聽取政府新聞發(fā)布會、媒體評論、互聯(lián)網(wǎng)討論，您可以發(fā)現(xiàn)，一個中文詞匯“預(yù)報”代表了地震監(jiān)測服務(wù)中的預(yù)測、預(yù)報、預(yù)警和警報系統(tǒng)。這種翻譯造成了混亂和誤解，官員和媒體的自相矛盾使情況變得更糟糕。結(jié)果，基于目前的科技能力，若有人說地震預(yù)報是不可能的（或有條件地部分可能），就可能被理解為地震預(yù)測和早期預(yù)警系統(tǒng)也不可能，而事實上，多年來，該兩者發(fā)揮了相當好的作用。 在討論5/12地震的時候，美國地質(zhì)觀測局（USGS）的科學(xué)家M·伯蘭彼德博士，向中國人民表示了深深的同情，同時，提供了有關(guān)地震預(yù)測和預(yù)報的翔實材料。正如他所說，此時此刻，對許多中國民眾來說，理解地震預(yù)報是一個非常重要的課題。 通過各種討論，本人發(fā)現(xiàn)，USGS的科學(xué)家顯得很保守和很小心，尤其是討論預(yù)報的時候、他們是極端地小心謹慎。對比之下，美國航天局（NASA）的科學(xué)家顯得更積極進取。事實上，USGS和NASA的地震預(yù)測工作，都做得很漂亮。本人相信，總有一天能實現(xiàn)更準確地預(yù)報大地震。不過，就目前而言，美國USGS的科學(xué)家有他們的充分理由選擇很保守的工作方式。 M·伯蘭彼德博士明確說明，“預(yù)測”和“預(yù)報”使用不同的方法來服務(wù)于不同的目的。這就是說，把“預(yù)測”和“預(yù)報”兩個意義不同的英文術(shù)語用一個中文詞匯“預(yù)報”表達，是制造混亂。5/12大地震說明，術(shù)語的準確翻譯是非常必要的，須知，只有對“預(yù)測”和“預(yù)報”的正確深入的了解、才能充分地受惠于地震監(jiān)測服務(wù)。 為此，這里與有興趣的讀者分享討論，后面是伯蘭彼德博士解釋說明的原文。若您需要音頻，您可以訪問如下USGS的網(wǎng)頁：《我們能預(yù)報地震嗎？》，地址是： http://www./corecast/details.asp?ID=76 附帶說明：在英文里，“forecast”和“prediction”是近義詞，都有對未來發(fā)生事件的估測的含義，但有明顯區(qū)別。譬如，就地震監(jiān)測服務(wù)來說，后面文字明白指明： ·“forecast”說明的是某段時間、某個區(qū)域和某個范圍震級的一組地震事件的趨勢，因而，它的概率取值傾向是“小概率”。地震監(jiān)測服務(wù)的“forecast”是完全可以做到的；實際上，美國等國家不但天天做、且每小時更新一次數(shù)據(jù)。 ·“prediction”說明的是特定時刻點、特定地點和特定震級的一個地震事件，帶有斷定性“預(yù)言”的色彩，因而，它的概率取值傾向是“大概率”。 做“prediction”的地震監(jiān)測是很困難的。 到目前，地震監(jiān)測中服務(wù)的“forecast”和“prediction”的英文術(shù)語，在中文里都用“預(yù)報”表達，結(jié)果造成概念混淆和誤解誤導(dǎo)。 伯蘭彼德博士解釋說明的原文: From: Michael Blanpied USGS Earthquake Hazards Program, Reston, Virginia, USA Date: Sat, 24 May 2008 11:42:58 -0400. Paul Spudich and I have discussed your correspondence about earthquake prediction, which is a very interesting subject and an important one to many Chinese at this moment. Responding to your first question: "If the above statement is true, then please explain the following rumors (successful earthquake forecasts with certain time and place) made by The Chinese State Seismological Bureau (including its local offices):" [*] Most American seismologists agree that the 1975 Haicheng earthquake was successfully predicted. A team of Canadian and Chinese scientists examined the events preceding the Haicheng earthquake and agreed with this assessment. Their study is published in an American seismological journal at: < http://bssa./cgi/content/abstract/96/3/757 >, and summarized in plain-English form in the magazine GeoTimes at: < http://www./june06/WebExtra062606.html >. Most American seismologists also agree that the Haicheng earthquake is the -only- successful prediction of a large earthquake. Despite decades of work and many attempts, using many methods, no other large earthquakes have been successfully predicted in the short term. Unlike most earthquakes, the Haicheng earthquake was preceded by hundreds of small foreshocks that made the prediction easier. Only a few big earthquakes have foreshocks, and it is extremely rare to have a strong sequence of foreshocks. Usually a foreshock cannot be distinguished from any of the other thousands of small earthquakes that happen every day. Unfortunately we have no information on the predictions of the other earthquakes that you listed, so cannot comment on them. You also asked: "If the statement is true, then the fact becomes: The USGS does not make earthquake predictions, but conducts forecasting, such as 50/30/10-years/probability-10% forecast and 24-hours forecasting nationwide. Correct or false?" You make a good point. In the U.S. the term ‘prediction‘ usually means a statement that an earthquake having a specified magnitude will occur in a short time interval (a day to a year), and in a well defined region (a city, county, or part of a U.S. state), and with a high probability much higher than the usual, day-to-day probability. The only U.S. prediction that has ever been endorsed by the USGS was that of the Parkfield earthquake; in that case a magnitude-6 earthquake was predicted to occur on a specific part of the San Andreas fault between 1985 and 1993. The earthquake occurred, but not until 2004. The U.S. public really wants us to predict earthquakes, and unfortunately most American seismologists (and the USGS) agree that we seismologists do not know how to make predictions with accuracies like the above definition. We are good at predicting the locations, magnitudes and shaking of future earthquakes, but we have no way to predict the time. The USGS uses the term ‘forecast‘ to mean a statement that an earthquake (or ground shaking) will occur in a specific place sometime during a longer time interval (5 - 50 years), usually at a much lower probability level. We cannot evacuate cites based on these forecasts because of the long time interval, but the public can use these forecasts to prepare their homes, offices, and factories for the future shaking. Such forecasts form the basis for improved building codes, insurance rates, city planning, and response planning. Note that seismologists usually use the word ‘earthquake‘ to mean slip on a fault (also called fault rupture); the public uses ‘earthquake‘ to mean ground shaking. The USGS forecasts both of these. Here are examples: So, for an example of a shaking forecast, see: <http://www.earthquake./research/hazmaps/products_data/1996/hazmaps/CAmap1r.gif> This is a map of California and Nevada that forecasts the strength of shaking (specifically the peak ground acceleration in % of g, the acceleration of gravity) that has a 90% chance of not being exceeded in 50 years. So, if you look at the intersection of the California, Nevada, and Oregon borders (at 42.0 degrees north, 120.0 degrees west), you will see that the map is yellow-green, which indicates that at that location there is a 90% probability that the ground motion will not exceed about 14% g (or a 10% probability that the shaking will exceed 14% g) sometime in the next 50 years. For an example of a forecast of slip (rupture) on faults, see: < http://www./core/public/sceccontext.php/3935/13661 > The colors on this California map represent the probabilities of having nearby (within about 6 km) fault slip during an earthquake of magnitude 6.7 or larger in the next 30 years. So the blue of Sacramento means that there is a 0.01% chance in the next 30 years that an earthquake fault within 6 km of Sacramento will slip in a magnitude 6.7 (or larger) earthquake. There is one time when we can say more specific things about the timing of earthquakes, and that is during aftershock sequences. We know very well that a large earthquake will generate many aftershocks, that the aftershock rate will generally decrease with time, and that there will generally be more smaller aftershocks and fewer large ones. We cannot predict the time or place of individual aftershocks, and we cannot predict how large the largest ones will be. For the state of California we publish a web map showing the probability of shaking from aftershocks and regular earthquakes in the next 24 hours: < http://pasadena.wr./step/ > The documentation is excellent, but I can briefly summarize here: The blue background shows the probability of a large earthquake in any 24 hours; this probability comes from observations of faults and past earthquakes and does not change. The yellow spots are areas of higher probability due to aftershocks of previous earthquakes; those spots typically fade away over a few days. Note that the 24-hour map cannot predict the time or place of a large earthquake, and the map does not use any observations other than small earthquakes. At this time we do not know of any method for predicting the time and place of an earthquake. # [*] The list of successful earthquake predictions (declared by CEA offices): - 02-04-1975, Haicheng, Liaoning; M=7.3. - 05-29-1976, 20:23, Longling county, Yunnan, M=7.3. - 07-28-1976, 3:00 AM, Qinglong County, Hebei Province. - 08-16-1976, Songpan-Pingjiang county, M=7.2. - 05-21-1984, Huanghai, Jiangsu, M=6.2. - 07-12-1995, morning, Menglian county, M=7.3. 來源：光明網(wǎng)博客>>zhiyan_blog 來源網(wǎng)址：http://blog.gmw.cn/u/36000/archives/2008/17460.html 2008.6.29.下載 |
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