Recurrent slow slip events as a barrier to the northward rupture propagation of the 2016 Pedernales earthquake (Central Ecuador)
Recurrent slow slip events as a barrier to the northward rupture propagation of the 2016 Pedernales earthquake (Central Ecuador)
复制标题
反复出现的慢滑移事件成为 2016 年佩德纳莱斯地震（厄瓜多尔中部）向北破裂传播的障碍
DOI：
10.1016/j.tecto.2017.12.012
复制
发表时间：
2017
期刊：
影响因子：
2.9
通讯作者：
M. Régnier
中科院分区：
文献类型：
--
作者：
Sandro Vaca;M. Vallée;J. Nocquet;J. Battaglia;M. Régnier
纳斯卡/南美洲俯冲带的北方厄瓜多尔段显示出空间不均匀的地震间耦合。两个高度耦合区（0.4° S-0.35° N和0.8° N-4.0° N）被一个低耦合区隔开，下文称为蓬塔加莱拉-蒙皮切区（PGMZ）。在1958年（Mw 7.7）和1979年（Mw 8.1）的耦合区内，北方板块和1942年（Mw 7.8）和2016年（Mw 7.8）的南部板块多次发生大的板间地震，而整个板块被认为在1906年的Mw 8.4-8.8大地震期间破裂。我们发现，在过去的十年中，PGMZ经历了定期和频繁的地震群。对于最好的记录序列（2013年12月至2014年1月），联合地震学和大地测量学分析揭示了与地震群相关的六周长的慢滑事件（SSE）。在此期间，微震活动被组织成与地震滑动的演变在空间和时间上相关的类似地震的家庭。在约60 × 40 km的区域内，释放的力矩（3.4 × 1018 Nm，Mw 6.3）远大于同一时期地震释放的力矩（5.8 × 1015 Nm，Mw 4.4）。2007-2008年，发生了类似的地震-地震事件，地震和地震过程的震级都较高。对15年来的地震波形进行互相关分析，进一步表明震群的重复时间为2年，这也意味着SSEs经常影响这一地区。这种SSE有助于释放累积的应力，这可能解释了为什么2016年的足目地震没有向北传播到PGMZ。
The northern Ecuador segment of the Nazca/South America subduction zone shows spatially heterogeneous interseismic coupling. Two highly coupled zones (0.4° S–0.35° N and 0.8° N–4.0° N) are separated by a low coupled area, hereafter referred to as the Punta Galera-Mompiche Zone (PGMZ). Large interplate earthquakes repeatedly occurred within the coupled zones in 1958 (Mw 7.7) and 1979 (Mw 8.1) for the northern patch and in 1942 (Mw 7.8) and 2016 (Mw 7.8) for the southern patch, while the whole segment is thought to have rupture during the 1906 Mw 8.4–8.8 great earthquake. We find that during the last decade, the PGMZ has experienced regular and frequent seismic swarms. For the best documented sequence (December 2013–January 2014), a joint seismological and geodetic analysis reveals a six-week-long Slow Slip Event (SSE) associated with a seismic swarm. During this period, the microseismicity is organized into families of similar earthquakes spatially and temporally correlated with the evolution of the aseismic slip. The moment release (3.4 × 1018Nm, Mw 6.3), over a ~ 60 × 40 km area, is considerably larger than the moment released by earthquakes (5.8 × 1015Nm, Mw 4.4) during the same time period. In 2007–2008, a similar seismic-aseismic episode occurred, with higher magnitudes both for the seismic and aseismic processes. Cross-correlation analyses of the seismic waveforms over a 15 years-long period further suggest a 2-year repeat time for seismic swarms, which also implies that SSEs recurrently affect this area. Such SSEs contribute to release the accumulated stress, likely explaining why the 2016 Pedernales earthquake did not propagate northward into the PGMZ.