Strain release at the trench during shallow slow slip: The example of Nicoya Peninsula, Costa Rica. Issue 10 (29th May 2017)

• Record Type: Journal Article
• Authors: Jiang, Yan; Liu, Zhen; Davis, Earl E.; Schwartz, Susan Y.; Dixon, Timothy H.; Voss, Nick; Malservisi, Rocco; Protti, Marino
• Is Part Of: Geophysical research letters. Volume 44:Issue 10(2017)
• Page Start: 4846
• Page End: 4854
• Publication Date: 2017-05-29
• Subjects: slow slip event -- seafloor geodesy -- subduction zone; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2017GL072803
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The near‐trench behavior of subduction megathrust faults is critical for understanding earthquake hazard and tsunami generation. The shallow subduction interface is typically located in unconsolidated sediments that are considered too weak to accumulate elastic strain. However, the spectrum of shallow fault slip behavior is still elusive, due in large part to the lack of near‐field observations. Here we combine measurements from seafloor pressure sensors near the trench and an onshore GPS network in a time‐dependent inversion to image the initiation and migration of a well‐documented slow slip event (SSE) in 2007 at the Nicoya Peninsula, Costa Rica. Our results show that the shallow SSE initiated on the shallow subduction interface at a depth of ~15 km, where pore fluid pressure is inferred to be high, and propagated all the way to the trench. The migrating event may have triggered a second subevent that occurred 1 month later. Our results document the release of elastic strain at the shallow part of the subduction megathrust and suggest prior accumulation of elastic strain. In conjunction with near‐trench shallow slow slip recently reported for the Hikurangi subduction zone and trench breaching ruptures revealed in some large earthquakes, our results suggest that near‐trench strain accumulation and release at the shallower portions of the subduction interface is more common than previously thought. Key Points: Slow slip events reach the trench off the Nicoya Peninsula Slow slip events initiate in areas of high pore fluid pressure Elastic strain accumulates in shallow parts of subduction zone