2023年2月23日出版的《JGR地球》杂志发表了科学家的一项最新研究成果。来自英国南安普顿大学的K. Leptokaropoulos课题组的最新研究报道了利用PI-LAB实验数据推断链变换断层的地震活动性质。

课题组研究人员使用海底地震仪(OBS)阵列记录1年局地地震活动(MC = 2.3以上的370次地震)和地球物理数据，研究位于赤道大西洋中部的链式转换的地震构造性质。该研究组通过考虑全球目录中更强的地震(MW≥5.0)来扩展他们的分析。基于历史事件分布、形态和海底地震仪地震活动的多维度分析，小组将链划分为东部、中部和西部三个区域。海底地震仪记录的地震活动最高的区域为链条东部地区，该区域具有菱形地形高地，负rMBA重力异常，只有少数历史MW≥5.5的事件。西部和中部地区海底地震仪地震活动性较低。

然而，根据海底地震仪和历史数据推断，这些区域容纳了大部分地震力矩释放。较高的b值与较低的rMBA和较浅的水深显著相关，可能与增厚的地壳有关。他们的结果表明,链上有很高的横向异质性。中低海底地震仪地震活动频度的地块偶尔会发生MW≥6.0级的地震，被海底地震仪活动丰富但5.5≤MW <6.0的历史事件较少的段所打断。这种分割可能是由于可变的流体循环和变化，也可能随着时间而变化。

附：英文原文

Title: Seismicity properties of the Chain Transform Fault inferred using data from the PI-LAB experiment

Author: K. Leptokaropoulos, C. A. Rychert, N. Harmon, J. M. Kendall

Issue&Volume: 2023-02-23

Abstract: Oceanic transform faults are intriguing in that they do not produce earthquakes as large as might be expected given their dimensions. We use 1-year of local seismicity (370 events above MC = 2.3) recorded on an array of ocean bottom seismometers (OBS) and geophysical data to study the seismotectonic properties of the Chain transform, located in the equatorial Mid-Atlantic. We extend our analysis back in time by considering stronger earthquakes (MW ≥ 5.0) from global catalogs. We divide Chain into three areas (east, central, and west) based on historical event distribution, morphology and multi-dimensional OBS seismicity cluster analysis. Seismic activity recorded by the OBS is the highest at the eastern area of Chain where there is a lozenge shaped topographic high, a negative rMBA gravity anomaly, and only a few historical MW ≥ 5.5 events. OBS seismicity rates are lower in the western and central areas. However, these areas accommodate the majority of seismic moment release, as inferred from both OBS and historical data. Higher b-values are significantly correlated with lower rMBA and with shallower bathymetry, potentially related to thickened crust. Our results suggest high lateral heterogeneity along Chain. Patches with moderate to low OBS seismicity rates that occasionally host MW ≥ 6.0 earthquakes are interrupted by segments with abundant OBS activity but few historical events with 5.5 ≤ MW < 6.0. This segmentation is possibly due to variable fluid circulation and alteration, which may also change in time.

DOI: 10.1029/2022JB024804

Source: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022JB024804