NEW SEISMIC GAP HYPOTHESIS - 5 YEARS AFTER
NEW SEISMIC GAP HYPOTHESIS - 5 YEARS AFTER
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DOI：
10.1029/94jb03014
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发表时间：
1995-03-10
影响因子：
3.9
通讯作者：
JACKSON, DD
中科院分区：
文献类型：
--
作者：
KAGAN, YY;JACKSON, DD
我们使用1989-1994年的地震数据来检验Nishenko基于地震空区理论的预测。我们将这一预测称为“新地震空区”假设，因为这是第一个基于地震空区假设的全球预测，该假设考虑了每个板块边界段特有的复发时间和特征地震震级。尼申科的预测给出了从1989年的第一天开始的5年、10年和20年内，大约100个区域中的每一个都将被特征地震填满的概率。现在只有第一个可以测试。我们使用了三个检验，基于（1）由特征地震填充的区域的总数，（2）观察到的填充区域列表将由具有Nishenko假设中指定的概率的过程产生的可能性，以及（3）与泊松零假设的李克奇比。零假设使用自1977年以来的地震活动性的平滑版本，并假设古腾堡-里克特震级分布。在我们的测试中，我们使用了哈佛矩张量仪和国家海洋和大气管理局对震中目录的初步确定。我们还在测试中使用了几个不同的震级截止值，因为Nishenko的预测没有明确说明特征地震震级和成功预测的阈值震级之间的关系。使用严格的解释，即只应计算等于或大于特征震级的地震，两个目录都显示预报覆盖的整个地区只有两次合格的地震。预测值为9.2，在99%的置信水平下，差异太大，不可能是偶然的。新的地震空区假说预测了太多的特征地震，原因有三。首先，对某些地区进行预测，特别是因为它们在过去的几个世纪中发生了两次或两次以上的地震，从而使估计的地震率产生偏差。第二，在计算重现率时，排除了第一个地震前和最后一个地震后的开放间隔。第三，预测假设每个区域的所有滑动都是在相同大小的特征地震中释放的，而实际上，无论是较小的还是较大的地震，都释放了相当大的滑动。观测到的地震规模分布与特征假设不一致：地震数量不是低于特征极限，而是根据标准的古腾堡-里克特关系分布。通过降低合格地震的震级阈值，有可能将观测到的地震和预测的地震数量之间的差异减少到可接受的水平。然而，对于我们尝试的每一个震级阈值，新的地震空区模型都未能通过填充数量的测试。
We use earthquake data from 1989-1994 to test a forecast by Nishenko based on the seismic gap theory. We refer to this forecast as the ''New Seismic Gap'' hypothesis, because it is the first global forecast based on the seismic gap hypothesis that considers the recurrence time and characteristic earthquake magnitude specific to each plate boundary segment. Nishenko's forecasts gave probabilities that each of about 100 zones would be filled by characteristic earthquakes during periods of 5, 10, and 20 years beginning on the first day of 1989. Only the first of these can be tested now. We used three tests based on (I) the total number of zones filled by characteristic earthquakes, (2) the likelihood that the observed List of filled zones would result from a process with the probabilities specified in Nishenko's hypothesis, and (3) the Likelihood ratio to that of a Poissonian null hypothesis. The null hypothesis uses a smoothed version of seismicity since 1977 and assumes a Gutenberg-Richter magnitude distribution. We used both the Harvard Centroid moment tenser and the National Oceanic and Atmospheric Administration preliminary determination of epicenters catalogs in our test. We also used several different magnitude cutoffs in our tests, because Nishenko's forecast did not specify a clear relationship between the characteristic earthquake magnitude and the threshold magnitude for a successful prediction. Using a strict interpretation, that only earthquakes equal to or larger than the characteristic magnitude should be counted, both catalogs show only two qualifying earthquakes in the entire area covered by the forecast. The predicted number is 9.2, and the discrepancy is too large to result from chance at the 99% confidence level. The new seismic gap hypothesis predicts too many characteristic earthquakes for three reasons. First, forecasts were made for some zones specifically because they had two or more earthquakes in the previous centuries, biasing the estimated earthquake rate. Second, open intervals before the first event and after the last event are excluded in calculation of recurrence rater Third, the forecast assumes that all slip in each zone is released in characteristic earthquakes of the same size, while in fact considerable slip is released by both smaller and larger earthquakes. The observed size distribution of earthquakes is inconsistent with the characteristic hypothesis: instead of a deficit of earthquakes above the characteristic limit, earthquake numbers are distributed according to the standard Gutenberg-Richter relation. By lowering the magnitude threshold for qualifying earthquakes, it is possible to reduce the discrepancy between the observed and predicted number of earthquakes to an acceptable level. However, for every magnitude threshold we tried, the new seismic gap model failed the test on the number of filled