Uplift rate transients at subduction margins due to earthquake clustering

Abstract

Coastal uplift is common in continental fore‐arc systems, with elevated paleoshorelines indicating that uplift rates can vary dramatically over time on individual margins. The origins of these changes in uplift rates are examined using a global data set of paleoshorelines together with 2‐D numerical models of subduction systems. Empirical paleoshoreline data (N = 282) from eight subduction margins indicate that uplift rates are generally not steady state and varied by up to a factor of 20 during the late Quaternary (≤125 ka). On many subduction margins uplift rates increase to the present day, a finding which we attribute to sampling bias toward those locations where Holocene uplift rates have been highest (with respect to other global margins which have undergone fast subsidence or no vertical motion—e.g., a property akin to the so‐called Sadler effect). Paleoshorelines and 2‐D models suggest that transient uplift rates at subduction margins are mainly a short‐term (<20 ka) phenomenon that cannot be accounted for by plate‐boundary scale processes such as changes in the rates of plate convergence, sediment underplating or isostatic unloading. Instead, time‐variable uplift rates are ascribed to temporal clustering of large‐magnitude earthquakes on upper plate faults and, to a lesser extent, the subduction thrust. The potential for future damaging earthquakes and tsunamis may have been underestimated at active subduction margins with no measureable Holocene uplift, and in such cases, late Quaternary paleoshorelines could provide an important constraint for hazard analysis.

Tectonic and Climatic Controls on the Spatial Distribution of Denudation Rates in Northern Chile (18°S to 23°S) Determined From Cosmogenic Nuclides

“…The EW faults are the longest at 19°S in the Rio Camarones drainage basin. Evidence for a temporal clustering of seismic activity (Mouslopoulou et al, ) and the occurrence of giant landslides at 19°S is suggested by previous work by Pinto et al () and Crosta et al (). The occurrence and concentration of mostly undated landslides could lead to the effect of 10 Be dissolution resulting in higher denudation rates in this setting.…”

Transient stripping of subducting slabs controls periodic forearc uplift

“…Marine terraces are also insightful markers for tracking coastal uplifts at intermediate timescales (i.e. 10 4 -10 6 years) with interpreted~10 4 -year-scale temporal variations proposed to relate to earthquake temporal clustering on upper-plate crustal faults 9 or cumulative megathrust earthquakes 8 . This transient signal is questioned by some authors that ascribe it to the uncertainty on age measurements of the terraces and to their .…”

“…anelastic) deformation. They include cumulative co-seismic slips on the subduction interface 7,8 and/or on forearc faults 9 and long-term aseismic processes, such as crustal deformation 10,11 and tectonic underplating [12][13][14][15][16] , both being partly driven by the frictional state of the underlying subduction interface 10,11,17,18 . However, the critical lack of constraints on the long-term (i.e.…”

Interseismic Loading of Subduction Megathrust Drives Long‐Term Uplift in Northern Chile

“…For instance, Melnick (2016) proposes that intermediate-depth earthquakes are responsible for the uplift of the northern Chilean coast while he discards the influence of interseismic fault locking. Other studies point to spatial relationships Geophysical Research Letters 10.1029/2019GL085377 between patterns of coupling coefficients and long-term features of the forearc in support of the influence of interseismic fault locking on topography building (Béjar-Pizarro et al, 2013;Mouslopoulou et al, 2016;Rousset et al, 2015;Saillard et al, 2017).…”