A Comprehensive Study of Precursory Quiescence Before Great and Large Earthquakes in the Central Aleutians and Chile

阿留申群岛中部地区发生了四次大规模地震 和智利瓦尔帕莱索地区。 所有这些事件 在他们之前报告了短暂的平静。 几项意见 据报告，这些地区发生的事件的前兆， 1971年反映了对彗星震级估计的系统性变化 而不是地震活动率的真实的变化。 其中包括：（1）两者 地震活动率下降可以观察到的地区， 2）地震带的分布特征; 智利地区在震级域的变化率可以很好地 （3）由于数量的变化， 阿留申群岛是强大的集与大小截止和弱的所有 事件，这是一个预期的幅度变化的特征。 的 年用于估计地震震级的台站平均数 智利小于10，可能太小，无法提供震级 其独立于站偏差。 我们建议重新确定 使用台站震级确定这些地区的震级 修正和重新检查地震活动模式之前， 大型事件，以确定报告的前兆是否是真实的， 由于系统性的大小变化。 我们计划将这些 从每个地区的当地地震台网数据进行观测， 增加我们对真实的星等分布的理解 如果存在的话，可能会有一些不确定的利率变化。 这项工作对于 了解这些事件之前存在哪些前兆。 更 重要的是，它对于了解 地震活动性数据的弱点，避免在地震活动性数据中出现严重错误。 解释这些数据用于地震预测。

Four large and great earthquakes have occurred in the Central Aleutians and Valparaiso, Chile regions since 1971. All of these events have had precursory quiescence reported prior to them. Several observations sugget that the reported precursors to events in these regions during 1971 reflect systematic changes in teleseismic magnitude estimates rather than real changes in seismicity rates. These include: 1) Both seismicity rate decreases can be observed in regions which are much larger than the rupture zones of the events; 2) the distribution of the rate changes in the Chile region in the magnitude domain can be well modeled as being due to changes in magnitudes; and 3) the change in the Aleutians is strong in sets with a magnitude cutoff and a weak in all events, a characteristic expected for changes in magnitudes. The average number of stations used for teleseismic magnitude estimates in Chile is less than 10, which is probably too small to provide magnitudes which are independent of station biases. We propose to redetermine the teleseismic magnitudes for these regions using station magnitude corrections and to re-examine the seismicity patterns prior to the large events to determine whether the reported precursors are real or due to systematic changes in magnitudes. We plan to integrate these observations with local seismic network data from each region to increase our understanding of the magnitude distribution of real precursory rate variations if they exist. This work is crucial for understanding what precursors exist prior to these events. More importantly, it is critical for understanding the strengths and weaknesses of seismicity data and avoiding making serious errors in interpreting these data for earthquake predictions.