U.S. Geological Survey, Pasadena, CA, USA.
Science. 2014 Feb 14;343(6172):762-4. doi: 10.1126/science.1248215. Epub 2014 Jan 23.
The extent to which ongoing seismicity in intraplate regions represents long-lived aftershock activity is unclear. We examined historical and instrumental seismicity in the New Madrid central U.S. region to determine whether present-day seismicity is composed predominantly of aftershocks of the 1811-1812 earthquake sequence. High aftershock productivity is required both to match the observation of multiple mainshocks and to explain the modern level of activity as aftershocks; synthetic sequences consistent with these observations substantially overpredict the number of events of magnitude ≥ 6 that were observed in the past 200 years. Our results imply that ongoing background seismicity in the New Madrid region is driven by ongoing strain accrual processes and that, despite low deformation rates, seismic activity in the zone is not decaying with time.
目前尚不清楚板内地区持续的地震活动在多大程度上代表长期余震活动。我们研究了美国新马德里中部地区的历史和仪器地震活动，以确定现今的地震活动是否主要由 1811-1812 年地震序列的余震组成。需要高的余震产率来匹配多次主震的观测结果，并将现代活动水平解释为余震；与这些观测结果一致的合成序列大大高估了过去 200 年中观测到的震级≥6 的事件数量。我们的结果表明，新马德里地区持续的背景地震活动是由正在积累的应变过程驱动的，尽管变形速率较低，但该地区的地震活动并没有随时间衰减。
