Are Creep Events Big? Estimations of Along-Strike Rupture Lengths
Are Creep Events Big? Estimations of Along-Strike Rupture Lengths
复制标题
蠕变事件大吗？
DOI：
10.1029/2021jb023001
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发表时间：
2022
期刊：
影响因子：
3.4
通讯作者：
Gittins D
中科院分区：
文献类型：
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作者：
Gittins D
许多断层的断层段被观测到在地表发生地震滑动。在圣安德烈亚斯断层的中央部分，滑动主要是在蠕变事件中积累的：每隔几周到几个月发生一次几毫米的滑动爆发。但是，尽管我们自20世纪60年代以来就在世界范围内观察到蠕变事件，我们仍然不知道大多数事件有多大，也不知道是什么力量驱动了它们。为了解决这种不确定性，我们系统地确定蠕变事件沿着中央圣安德烈亚斯断层，并确定其沿着走向破裂范围。我们首先使用互相关和目视检查来识别单个蠕变计的事件。利用18台USGS蠕变仪的数据，我们确定了1985年至2020年期间的2120条蠕变事件记录。然后，我们搜索的滑动，是密切定时跨多个蠕变计。我们确定了306例紧密定时滑动，这可能表明306蠕变事件，破裂多个蠕变计的位置。通过目视检查和时间统计分析，我们识别出了各种蠕变事件类型，包括单蠕变仪事件、小型（<2 km）事件、中型（3-6 km）事件、大型（>10 km）事件以及断裂多条断层链的事件。许多大型（几公里）事件的存在表明，蠕变事件不是由降雨相关的小扰动产生的;它们更可能是由复杂或异质摩擦弱化驱动的，它们可能为圣安德烈亚斯断层上更大规模滑动的动力学提供了一个窗口。
Segments of many faults are observed to slip aseismically at the surface. On the central segment of the San Andreas Fault, aseismic slip accumulates largely in creep events: few mm bursts of slip which occur every few weeks to months. But even though we have observed creep events worldwide since the 1960s, we still do not know how big most events are or which forces drive them. To address this uncertainty, we systematically identify creep events along the central San Andreas Fault and determine their along‐strike rupture extents. We first use cross‐correlation and visual inspection to identify events at individual creepmeters. With data from 18 USGS creepmeters, we identify 2120 records of creep events between 1985 and 2020. We then search for slip that is closely timed across multiple creepmeters. We identify 306 instances of closely timed slip, which could indicate 306 creep events that rupture multiple creepmeter locations. Through visual inspection and statistical analysis of timing, we identify a variety of creep event types, including single‐creepmeter events, small (<2 km) events, medium‐sized (3–6 km) events, large (>10 km) events, and events that rupture multiple fault strands. The existence of many large (few‐km) events suggests that creep events are not produced by small, rainfall‐associated perturbations; they are more likely driven by complex or heterogeneous frictional weakening and they may provide a window into the dynamics of a larger scale slip on the San Andreas Fault.