We report the first paleoseismic evidence jointly documenting coseismic subsidence and tsunami inundation from the 1730 Chile earthquake (Mw >= 9) and its trans-Pacific tsunami. At Campiche, a former coastal lagoon in Chile's Metropolitan Region, multiproxy stratigraphic, sedimentological, and microfossil data reveal a laterally continuous tsunami sand sheet that extends similar to 2 km inland, sharply disrupts lagoonal mud, and shows an erosional lower contact, rip-up clasts, and mud drapes from waning flow. Accompanying shifts from freshwater to brackish-marine diatom assemblages and the sudden appearance of salt-tolerant plant remains record a persistent increase in tidal influence, indicating coseismic subsidence. Radiocarbon and luminescence ages constrain its deposition to 1698-1782 CE, consistent with historical accounts of the 1730 tsunami and the absence of any other comparable event in the written record. Campiche thus complements previously reported uplift-dominated mid-Holocene records by showing that infrequent, subsidence-generating shallow ruptures-not just deeper, uplift-producing earthquakes-are an integral component of central Chile's megathrust behavior. Remarkably, this paleoseismic archive, formed during a brief window within a similar to 4000-year marine-to-terrestrial transition and preserved in an emergent, semiarid, preservation-limited margin, suggests that similar evidence may exist in other unfavorable settings. Integration of the Campiche record with historical, geophysical, and geodetic data indicates that a shallow slip deficit of similar to 20 m may have accumulated since 1730, consistent with highly coupled shallow asperities, the recent shift from coastal stability to gradual subsidence, and proposed 200-650 yr recurrence intervals for large tsunamis. Taken together, these lines of evidence suggest that Chile's Metropolitan Region now lies within a plausible near-term window for another large tsunamigenic rupture. These findings underscore the need to integrate paleoseismic records and deep-shallow rupture interplay-including infrequent shallow Mw >= 9 events superimposed on more frequent Mw similar to 8 deeper earthquakes-into tsunami-hazard models for Chile and the wider Pacific.

Characterizing the spatial distribution of ruptures from historical and recent earthquakes is key to understanding the seismic cycle of large earthquakes in subduction zones, and thus to assessing the potentialrisks associated with future earthquakes. Central Chile (35°S - 38°S) has been continuously affected by large earthquakes, such as the 2010 Maule (Mw 8.8) and the 1835 earthquakes witnessed by Robert Fitzroy (HMS Beagle captain). Here, we identify the rupture pattern and tsunami propagation of the 1751, 1835, and 2010 mega-earthquakes, events that overlapped in central Chile, by compiling historical records and applying robust statistical tools. We used an adaptation of a logic tree methodology to generate random sources of slip distribution for each event, constrained by tsunami and deformation data. We find that the three events studied have different slip peaks. The 1751 earthquake has the largest slip with a maximum patch of ∼ 26 m, while the 2010 and 1835 earthquakes reach slips of ∼ 16 m and ∼ 10 m, respectively. Our results show that a part of the segment between 36◦S and 37◦S was consistently affected by large earthquakes, but with different slip and depth. The northern part of the segment accumulated energy for at least 300 years and was released by the 2010 earthquake. This work provides important information for identifying rupture patterns between historical and recent earthquakes, and highlights the importance of extending the time scale of earthquake slip distribution analyses to multiple cycles to describe both earthquake characteristics and their spatial relationship, and thus gain a better understanding of seismic hazard.

The removal of Glines Canyon Dam on the Elwha River in western Washington, USA, from 2011 to 2014 introduced a 20-Mt pulse of stored sediment and logs into the downstream channel. We used terrestrial laser scanning, high-resolution orthoimages, and surveys of large wood (LW) and sediment grain-size distribution to quantify changes to the channel and LW in four different geomorphic settings spanning a 16-year period before, during, and after dam removal. The results provide insights into the role of site-specific geomorphology on the interplay among sediment size and supply, wood, and channel form in the aftermath of a dam removal. Sediment-size distribution, braiding index, and number of log jams rapidly reached new steady states. Other factors, such as channel sinuosity and log jam area, were still evolving six years after the dam was removed. The rate and type of river response was partially dictated by the geomorphic setting and the accumulation of LW. Complex reaches trapped more sediment and LW, initiating immediate changes in the channel count, position and lateral migration that continued to evolve through positive feedbacks. Single-channel sites experienced less initial erosion and deposition, but channel migration continued for years once it was underway. The post-dam sediment composition progressively shifted to a mixed size distribution midway between the armored cobbles when the dam was in place and the influx of primarily sand and fine gravel during dam removal. Reworking of sediment was most rapid in the first year after dam removal, especially at the site with the greatest channel complexity. The relation between log jams and channel divisions fundamentally changed. There were 11 log jams in the middle reach of the Elwha River downstream of Glines Canyon Dam, and all log jams associated with channel divisions occurred at the heads of stable, vegetated islands. During dam removal, the number of log jams rapidly increased to 86 and stabilized near that level in the post-dam period. While log jams on stable islands persisted, more were added at divisions around transient sediment bars, scattered across gravel bars, or outside of the active channel. Following a brief spike during dam removal, there was a net long-term increase of similar to 10 % in the number of channel divisions associated with log jams. The sediment deposits, LW, vegetation, channel morphology and river discharge continued to cause adjustments within the fluvial system a decade after the start of dam removal. This state of greater variability could be the new equilibrium for years to come.

Characterizing the spatial distribution of ruptures from historical and recent earthquakes is key to understanding the seismic cycle of large earthquakes in subduction zones, and thus to assessing the potential risks associated with future earthquakes. Central Chile (35 ^∘ S–38 ^∘ S) has been repeatedly affected by large earthquakes, such as the 2010 Maule (Mw 8.8) and the 1835 earthquakes witnessed by Robert Fitzroy (HMS Beagle captain). Here, we identify the rupture pattern and tsunami propagation of the 1751, 1835, and 2010 mega-earthquakes, events that overlapped in central Chile, by compiling historical records and applying robust statistical tools. We used an adaptation of a logic tree methodology to generate random sources of slip distribution for each event, constrained by tsunami and vertical deformation data. We find that the three events studied have different slip peaks. The 1751 earthquake has the largest slip with a maximum patch of ∼ 26 m, while the 2010 and 1835 earthquakes reach slips of ∼ 16 m and ∼ 10 m, respectively. Our results show that a part of the margin between 36 ^∘ S and 37 ^∘ S was consistently affected by large earthquakes, but with different slip and depth. The shallower depths of the megathrust north of 36 ^∘ S accumulated energy for at least 300 years, which was released by the 2010 earthquake. Our results provide important constraint for rupture patterns and spatial relationships between historical and recent earthquakes, thus extending the time scale for seismic slip distribution analyses over multiple cycles and contributing to a more comprehensive understanding of seismic hazards.

The tsunami associated with the giant 9.5 M-w 1960 Chile earthquake deposited an extensive sand layer above organic-rich soils near Queule (39.3 degrees S, 73.2 degrees W), south-central Chile. Using the 1960 tsunami deposits, together with eye-witness observations and numerical simulations of tsunami inundation, we tested the tsunami inundation sensitivity of the site to different earthquake slip distributions. Stratigraphically below the 1960 deposit are two additional widespread sand layers interpreted as tsunami deposits with maximum ages of 4960-4520 and 5930-5740 cal BP. This >4500-year gap of tsunami deposits preserved in the stratigraphic record is inconsistent with written and geological records of large tsunamis in south-central Chile in 1575, 1837, and possibly 1737. We explain this discrepancy by: (1) poor preservation of tsunami deposits due to reduced accommodation space from relative sea-level fall during the late Holocene; (2) recently evolved coastal geomorphology that increased sediment availability for tsunami deposit formation in 1960; and/or (3) the possibility that the 1960 tsunami was significantly larger at this particular location than other tsunamis in the past >4500 years. Our research illustrates the complexities of reconstructing a complete stratigraphic record of past tsunamis from a single site for tsunami hazard assessment.

On September 16, 2015, a Mw 8.3 earthquake struck the north-central Chile coast, triggering a tsunami observed along 500 km of coastline, between Huasco (28.5 degrees S) and San Antonio (33.5 degrees S). This tsunami provided a unique opportunity to examine the nature of tsunami deposits in a semi-arid, siliciclastic environment where stratigraphic and sedimentological records of past tsunamis are difficult to distinguish. To improve our ability to identify such evidence, we targeted one of the few low-energy, organicrich depositional environments in north-central Chile: Pachingo marsh in Tongoy Bay (30.3 degrees S). We found sedimentary evidence of the 2015 and one previous tsunami as tabular sand sheets. Both deposits are composed of poorly to moderately sorted, gray-brown, fine-to medium-grained sand and are distinct from underlying and overlying organic-rich silt. Both sand beds thin (from similar to 20 cm to <1 cm) and fine landward, and show normal grading. The older sand bed is thicker and extends over 125 m further inland than the 2015 tsunami deposit. To model the relative size of the tsunamis that deposited each sand bed, we employed tsunami flow inversion. Our results show that the older sand bed was produced by higher flow speeds and depths than those in 2015. Anthropogenic evidence along with Cs-137 and Pb-210 dating constrains the age of the older tsunami to the last similar to 110 years. We suggest that the older sand bed was deposited by the large tsunami in 1922 CE sourced to the north of our study site. This deposit represents the first geologic evidence of a pre-2015 tsunami along the semi-arid north-central Chile coast and highlights the current and continuing tsunami hazard in the region. (C) 2021 The Authors. Published by Elsevier Ltd.

The Elwha River once provided vital habitat for a variety of salmonid species, but after two dams were emplaced on the river in the early 1900s, habitat diminished, and salmon populations declined.From 2011-2014, the dams were finally removed to restore the Elwha ecosystem.To understand the long-term geomorphic impacts of the Glines Canyon Dam removal on the Elwha River, I quantified changes in four parameters: inchannel large wood, main channel sinuosity, channel braiding, and sedimentation.Highresolution imagery from 2012-2020 was used to map large wood and digitize main and secondary river channels, and field surveys were completed at study sites to assess sediment-size distribution six years after the completion of the dam removal.Analysis of large wood revealed that the number of individual logs peaked during the dam removal but decreased after the removal and remained low.Logjam area increased steadily throughout the eight-year study period while the number of logjams stayed constant, suggesting that individual logs were recruited into existing logjams over time.Main channel sinuosity increased during and after the removal.After peaking in 2017, sinuosity decreased but has yet to return to conditions present before the dam removal.iv Channel braiding peaked during the dam removal process, dropped, and remained relatively consistent for the remainder of the study period, reaching an equilibrium state that is more braided than before the dam removal.Six years after the completion of the dam removal, sediment bars contain a mixture of grain sizes, in contrast to the armored, coarse sediment when the dam was in place or the blanket of fine sediment released during the dam removal.The results demonstrate the complexity and interconnectedness of various geomorphic and ecological parameters and suggest that while some geomorphic parameters may establish a new equilibrium in the years following a dam removal, others will continue to evolve over longer timescales.

Understanding sedimentation patterns in small coastal watersheds due to landscape perturbations is critical for connecting hillslope and fluvial processes, in addition to managing aquatic habitats for anadromous fish and other aquatic species in the Oregon Coast Range (OCR). Changes in sedimentation patterns spanning the last 250 years are preserved in two landslide-dammed lakes in small watersheds (< 10 km(2)) underlain by the Tyee Formation in the central OCR. Dendrochronology of drowned Douglas-fir stumps in both lakes provided precise timing of the damming and formation of the lakes, with Klickitat Lake forming in winter ad 1751/52 and Wasson Lake in winter ad 1819/20. Perturbations from wildfires, logging and road development, and previously underappreciated snow events affect sedimentation rates in the lakes to different degrees, and are identified in the sediment record using cesium-137 (Cs-137), high-resolution charcoal stratigraphy, local fire records, and aerial photography. Each lake has variable sedimentation accumulation rates (0.05-4.4 cm yr(-1)) and mass accumulation rates (0.02-1.42 g cm(-2) yr(-1)). Sedimentation rates remained low from the landslide-damming events until the mid-19th century, when they increased following stand-replacing wildfires. Aside from a sediment remobilization triggered by human modification of the landslide dam at Klickitat Lake around 1960, the largest peaks in mass accumulation rates in the mid-20th century at both lakes in the early 1950s precede major road construction and logging activity in the watersheds. Subsequent sedimentation rates are lower, but variable, and possible effects of logging and road development might be exacerbated by abnormal precipitation and heavy snow events. A comparison of previous studies of landslide-dammed lakes in larger watershed of the OCR are consistent with our findings of increased sedimentation in the mid-20th century, as well as higher sedimentation rates in the debris-flow dominated southern Tyee Formation than in the lower-relief northern Tyee Formation.

Earth Surface Processes and LandformsVolume 46, Issue 15 p. 3011-3015 ESEX COMMENTARY Accept and support a multi-thread career path to keep women in the academic stream Sara L. Rathburn, Corresponding Author Sara L. Rathburn sara.rathburn@colostate.edu orcid.org/0000-0002-2514-4823 Department of Geosciences, Colorado State University, Fort Collins, CO, USA Correspondence Sara L. Rathburn, Professor, Department of Geosciences, 1482 Campus Delivery, Fort Collins, CO 80523-1482, USA. Email: sara.rathburn@colostate.eduSearch for more papers by this authorLisa L. Ely, Lisa L. Ely orcid.org/0000-0002-1892-8339 Department of Geological Sciences, Central Washington University, Ellensburg, WA, USASearch for more papers by this author Sara L. Rathburn, Corresponding Author Sara L. Rathburn sara.rathburn@colostate.edu orcid.org/0000-0002-2514-4823 Department of Geosciences, Colorado State University, Fort Collins, CO, USA Correspondence Sara L. Rathburn, Professor, Department of Geosciences, 1482 Campus Delivery, Fort Collins, CO 80523-1482, USA. Email: sara.rathburn@colostate.eduSearch for more papers by this authorLisa L. Ely, Lisa L. Ely orcid.org/0000-0002-1892-8339 Department of Geological Sciences, Central Washington University, Ellensburg, WA, USASearch for more papers by this author First published: 27 October 2021 https://doi.org/10.1002/esp.5281Citations: 1Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Open Research DATA AVAILABILITY STATEMENT No original data included. Citing Literature Volume46, Issue15December 2021Pages 3011-3015 RelatedInformation

We present a comprehensive relative sea-level (RSL) database for north, central, and south-central Chile (18.5 degrees S - 43.6 degrees S) using a consistent, systematic, and internationally comparable approach. Despite its latitudinal extent, this coastline has received little rigorous or systematic attention and details of its RSL history remain largely unexplored. To address this knowledge gap, we re-evaluate the geological context and age of previously published sea-level indicators, providing 78 index points and 84 marine or terrestrial limiting points spanning from 11 ka to the present day. Many data points were originally collected for research in other fields and have not previously been examined for the information they provide on sea-level change. Additionally, we describe new sea-level data from four sites located between the Gulf of Arauco and Valdivia. By compiling RSL histories for 11 different regions, we summarise current knowledge of Chilean RSL. These histories indicate mid Holocene sea levels above present in all regions, but at highly contrasting elevations from similar to 30 m to <5 m. We compare the spatiotemporal distribution of sea-level data points with a suite of glacial isostatic adjustment models and place first-order constraints on the influence of tectonic processes over 10(3)-10(4) year timescales. While seven regions indicate uplift rates <1 m ka(-1), the remaining regions may experience substantially higher rates. In addition to enabling discussion of the factors driving sea-level change, our compilation provides a resource to assist attempts to understand the distribution of archaeological, palaeoclimatic, and palaeoseismic evidence in the coastal zone and highlights directions for future sea-level research in Chile. (C) 2020 Elsevier Ltd. All rights reserved.

Reliable tsunami early warning forecasts rely on accurate initial modeling conditions and interpretations of subduction zone behavior in a multi-century perspective.GPS and seismologic data were introduced this past century to study rupture dynamics in detail, however limited information is known about ruptures that pre-date the 20 th century.I propose a methodology that uses statistics to better understand these pre-20 th century ruptures.This methodology applies the historical and geologic tsunami record as a means to select a suite of tsunami simulations from earthquake source solutions.I chose south-central Chile (46°S to 30°S) to test this new methodology; it has an extensive earthquake historical record at 47 different coastal sites, some of which date to the 16 th century.Between 1570 and 1960, this region experienced at least 17 tsunamigenic earthquakes.In addition to evaluating possible source solutions for these earthquakes, my methodology also allows the test of whether subducted fracture zones, like the Mocha fracture zone (MFZ) in south-central Chile, controls rupture propagation (as previously hypothesized).For this research, I used GeoClaw, a numerical tsunami modeling code, to simulate 423 forward-modeled M w iv 8.7 -9.5 earthquake scenarios with stochastic, variable slip distributions.I used Akaike's Information Criterion (AIC) to identify significant earthquake parameters (M w and slip location) of 17 events by statistically selecting source models that had similar simulated wave heights to known observations in the historic and geologic record.For example, I concluded from AIC that the 1960 event was a M w 9.3 rupture with high slip concentration (~ 30 m) at ~ 39-40ºS, and the 1730 event was a M w 9.3 rupture with shallow maximum slip at ~ 36ºS; both solutions support the MFZ hypothesis.The AIC results generally agree with previously estimated magnitudes within the literature and were validated by using root mean square error RMSE values.I produced high resolution maps at three coastal sites with well-known tsunami observations for further refinement of potential rupture scenarios.Defining historical rupture characteristics gives insight regarding temporal and spatial variabilities of locking zones.This information may be useful for predicting future near-field tsunami wave heights for particularly vulnerable coastal regions.