Interseismic Megathrust Coupling at the Osa Peninsula, Costa Rica

IF 3.9 2区 地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS
Mason Perry, Cyril Muller, Marino Protti, Lujia Feng, Emma M. Hill
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Abstract

At the Osa Peninsula in southern Costa Rica, magnitude >7 earthquakes have been generated along the Middle American trench in 1904, 1941, and 1983 following a ∼40-year recurrence interval, suggesting a rupture may be impending. However, regional interseismic coupling remains poorly constrained, largely due to sparse observations that are likely contaminated by aliasing effects of repeating shallow slow slip events (SSEs) that occur roughly every 4 years, but were only discovered recently. These SSEs, while likely reducing megathrust coupling near the trench, may load or trigger the next rupture of the 1983 asperity. Using new continuous Global Navigation Satellite System (GNSS) data from an updated and densified regional network, we derive inter-SSE rates of deformation and invert for slip deficit and megathrust coupling along the Middle American Trench, implementing block modeling to correct for the motion of the Panama microplate. We invert for slow slip and remove a time-averaged estimate of cumulative slow slip from our models. Our results indicate that the region of highest inter-SSE coupling (>0.8) corresponds with the spatial extent of SSE slip. We also find that SSEs are sufficient to release nearly all the elastic strain accumulated over their 4-year recurrence interval in localized regions. Accounting for this, in the region immediately downdip of the slow slip patch—the same region thought to have ruptured in the 1983 Mw 7.4 event—we estimate an interseismic coupling ratio of ∼0.5–0.7 corresponding to ∼1.75–2 m of accumulated slip deficit since 1983, sufficient to generate a similar magnitude rupture in the future.

Abstract Image

哥斯达黎加奥萨半岛的地震间大逆冲耦合
在哥斯达黎加南部的奥萨半岛,沿中美洲海沟在1904年、1941年和1983年发生了7级地震,间隔约40年,这表明破裂可能即将发生。然而,区域地震间耦合的约束仍然很差,很大程度上是由于稀疏的观测结果可能受到重复的浅层慢滑事件(sse)的混叠效应的污染,这些事件大约每4年发生一次,但最近才发现。这些sse虽然可能会减少海沟附近的大型逆冲耦合,但可能会加载或触发1983年粗糙体的下一次破裂。利用来自更新和密集区域网络的新的连续全球导航卫星系统(GNSS)数据,我们推导了沿中美洲海沟的sse间变形率和逆滑亏损和大逆冲耦合,并实施了块体建模来校正巴拿马微板块的运动。我们对慢滑进行反演,并从我们的模型中去除累积慢滑的时间平均估计。结果表明,SSE间耦合最大的区域(>0.8)与SSE滑移的空间范围相对应。我们还发现,在局部区域,sse足以释放在其4年复发间隔内积累的几乎所有弹性应变。考虑到这一点,在慢滑块立即下降的区域(即1983年Mw 7.4事件中被认为破裂的同一区域),我们估计地震间耦合比为~ 0.5-0.7,对应于自1983年以来累积的滑移亏损~ 1.75-2 m,足以在未来产生类似震级的破裂。
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来源期刊
Journal of Geophysical Research: Solid Earth
Journal of Geophysical Research: Solid Earth Earth and Planetary Sciences-Geophysics
CiteScore
7.50
自引率
15.40%
发文量
559
期刊介绍: The Journal of Geophysical Research: Solid Earth serves as the premier publication for the breadth of solid Earth geophysics including (in alphabetical order): electromagnetic methods; exploration geophysics; geodesy and gravity; geodynamics, rheology, and plate kinematics; geomagnetism and paleomagnetism; hydrogeophysics; Instruments, techniques, and models; solid Earth interactions with the cryosphere, atmosphere, oceans, and climate; marine geology and geophysics; natural and anthropogenic hazards; near surface geophysics; petrology, geochemistry, and mineralogy; planet Earth physics and chemistry; rock mechanics and deformation; seismology; tectonophysics; and volcanology. JGR: Solid Earth has long distinguished itself as the venue for publication of Research Articles backed solidly by data and as well as presenting theoretical and numerical developments with broad applications. Research Articles published in JGR: Solid Earth have had long-term impacts in their fields. JGR: Solid Earth provides a venue for special issues and special themes based on conferences, workshops, and community initiatives. JGR: Solid Earth also publishes Commentaries on research and emerging trends in the field; these are commissioned by the editors, and suggestion are welcome.
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