An important first step in the geotechnical asset management of Great Smoky Mountains National Park (GRSM) is the creation of an unstable slope inventory along major transportation corridors. Slope-stability problems are frequent in GRSM, often initiated in highly weathered and fractured metasedimentary rocks. In this study, an unstable slope inventory was created using the Unstable Slope Management Program for Federal Land Management Agencies protocols. Hazards and risks were evaluated for 285 unstable slopes along 243.67 km of roadway. Kernel density estimation was used to identify unstable slope hotspots and establish 14 sites for site-specific investigations to evaluate potential impacts of discrete unstable slopes along major roadways. Two-dimensional probabilistic rockfall simulations and acid-base accounting tests were used to predict rockfall pathways and evaluate the acid-producing potential of rocks. Simulations indicated that rock material would likely enter the roadway at all 14 sites. Acid-base accounting test results indicated that slaty rocks of the Anakeesta Formation and graphitic schist of the Wehutty Formation are primary acid-producing rocks in rockfall-prone areas. This research illustrates an approach for prioritizing areas for site-specific investigations towards the goal of improving safety in GRSM, including developing mitigation strategies for rockfall by widening ditches, installing barriers, and encapsulating acidic rockfall material.

The October 17th, 2015 Taan Fiord landslide and tsunami generated a runup of 193 m, nearly an order of magnitude greater than most previously surveyed tsunamis. To date, most post-tsunami surveys are from earthquake-generated tsunamis and the geomorphic signatures of landslide tsunamis or their potential for preservation are largely uncharacterized. Additionally, clear modifications described during previous post-tsunami surveys are often ephemeral and unlikely to be preserved. Documented geomorphic modifications of several low gradient fan deltas within Taan Fiord make it an excellent laboratory for characterizing signatures of a landslide tsunami event. Geomorphic changes to fan deltas in Taan Fiord caused by the landslide-generated tsunami included complete vegetation loss over more than 0.6 km(2) of fan surfaces, formation of steep fan front scarps up to 10 m high, extensive local alterations of fan topography, and formation of new tsunami return-flow channels. Two relatively stable fan deltas in Taan Fiord were heavily vegetated prior to the Taan event and may preserve features of tsunami modification for decades to centuries. If this is the case, fan deltas may be a previously unrecognized location for preservation of tsunami signatures in the recent past. Fans in poorly monitored regions, such as Greenland, could thus hold evidence of previously unidentified recent landslide tsunami events. (C) 2019 Elsevier B.V. All rights reserved.

Glacial retreat in recent decades has exposed unstable slopes and allowed deep water to extend beneath some of those slopes. Slope failure at the terminus of Tyndall Glacier on 17 October 2015 sent 180 million tons of rock into Taan Fiord, Alaska. The resulting tsunami reached elevations as high as 193 m, one of the highest tsunami runups ever documented worldwide. Precursory deformation began decades before failure, and the event left a distinct sedimentary record, showing that geologic evidence can help understand past occurrences of similar events, and might provide forewarning. The event was detected within hours through automated seismological techniques, which also estimated the mass and direction of the slide - all of which were later confirmed by remote sensing. Our field observations provide a benchmark for modeling landslide and tsunami hazards. Inverse and forward modeling can provide the framework of a detailed understanding of the geologic and hazards implications of similar events. Our results call attention to an indirect effect of climate change that is increasing the frequency and magnitude of natural hazards near glaciated mountains.

The purpose of this study was to characterize the rock mass at Mount Rushmore National Memorial (MORU) and to evaluate the stability of the presidential sculptures. The sculptures are carved in granite, but quartz-mica schist and minor outcrops of pegmatite are also present within the site area. We divided the MORU area into four “regions” to collect discontinuity data. Since the sculptures were not accessible during this study, we used light detection and ranging (LiDAR) data and Split-FX software to determine the orientations of both the discontinuities and the slopes on the sculptures. The rock mass characterization results, using both the Rock Mass Rating system and the Q-system, indicate the granite, schist, and pegmatite classify as fair to good rock. Kinematic analysis results indicate that the potential for planar, wedge, and toppling failures exists for various slopes on each of the sculptures. The factor of safety (FS) values against planar and wedge sliding, ignoring cohesion, range from 0.1 to 0.8 and from 0.2 to 1.3, respectively. Since failures have not been observed at the memorial, we back-calculated the amount of cohesion required to raise the FS values to >1. The back-calculation results show that both cohesion and friction contribute to stability of the sculptures. Using the Slide program, we performed an overall slope probabilistic analysis for the slopes on which the MORU sculptures are located. The analysis determines the mean factor of safety (FSM), reliability index (RI), and probability of failure (PF) for the slopes. For the static condition, the analysis resulted in FSM, RI, and PF values ranging from 3.3 to 4.5 percent, 3.3 to 7.8 percent, and 0 percent, respectively. With a seismic load coefficient of 0.14 applied to the slopes, the corresponding values were: 2.6 to 4.1 percent, 2.9 to 4.7 percent, and 0 percent. For both the static and seismic conditions, the results indicate that, overall, the slopes of the sculptures are stable.

During an extreme storm in the Colorado Front Range in September 2013, 11 debris flows initiated at high elevations in Rocky Mountain National Park. We characterized these debris flows to determine controls on their initiation and found that eight of the 11 initiated in areas of convergent topography, and eight initiated at elevations > 2800 m. The high proportion of debris flows in areas of convergent topography emphasizes the importance of local topographic control on initiation. Debris flows at high elevations in the Front Range are atypical; this event broadens our understanding of debris flow regimes in the Front Range. Survey data (scarp dimensions, transport distance) suggest that transport is influenced by downslope processes rather than characteristics of the initiation site. At one site with evidence of multiple debris flows sourced from the same colluvial hollow, we obtained relative ages of debris flow deposits through geomorphic mapping and fan stratigraphy. We used radiocarbon and beryllium-10 (Be-10) analysis to age stratigraphic deposits and debris flow levees. Radiocarbon ages (n = 6) were highly variable and were interpreted to reflect secondary hillslope processes rather than debris flow ages. Large ranges in cosmogenic exposure age and anomalously old samples indicate that sampled boulders (n = 14) contained inherited Be-10 concentrations. Beryllium-10 concentrations were likely acquired as exposed bedrock surfaces or during intermediate storage in the colluvial hollow. We suggest that Be-10 inheritance limits the utility of cosmogenic exposure dating of debris flows with short transport distances (10(-1) to 10(1) km). Despite these limitations, we documented field evidence for four to seven debris flows in the last 75 ka, including two in the last 8 ka. Considered collectively, Be-10 sample ages from all levees suggest that greatest sediment production occurred during Quaternary glacial stages due to periglacial processes. Subsequent evacuation of the colluvial hollow likely occurred during wetter periods of the mid-Holocene. (c) 2018 John Wiley & Sons, Ltd.

A fundamental goal of the Earth Science community is to understand how perturbations on Earth's surface are preserved in the stratigraphic record. Recent Source to Sink (S2S) studies of the Waipaoa Sedimentary System (WSS), New Zealand, are synthesized herein to provide a holistic perspective of the processes that generate, transport and preserve sedimentary strata and organic carbon on the Waipaoa margin in the late Quaternary. Rapid uplift associated with subduction processes and weak sedimentary units have conspired to generate rapid rates of incision and erosion in the Waipaoa catchment since the Last Glacial Maximum (LGM). We show that although much of the sediment exported offshore during this time interval originated from valley excavation, a substantial portion emanated from hillslopes, mostly through deep-seated landslide and earthflow processes that were vigorous during periods of rapid fluvial incision just prior to the Pleistocene-Holocene transition. Lacustrine sediments deposited in naturally-dammed 7-ky-old Lake Tutira provide a record of Holocene environmental controls on upper catchment sedimentation in the WSS, with 1400 storms identified. Storm frequency is modulated by the waxing and waning of atmospheric teleconnections between the tropics and Antarctica. Furthermore, clear long-term changes in sediment yield are evident from the Lake Tutira record following human settlement as conversion to pasture is accompanied by a 3-fold increase in the long-term lake sediment accumulation rate.Whereas there is ample evidence that Waipaoa River flood deposits are routinely deposited offshore in the sheltered confines of Poverty Bay, over the longer term, waves and currents subsequently resuspend and transport these deposits both landward (sandy fraction) and seaward (finer fraction). Thus, the timing of sediment supply to areas of net sediment accumulation is more often driven by wave events that are not associated with river flooding. Therefore, we conclude that asynchronicity of river-sediment delivery and of wave resuspension in most instances precludes the direct preservation of flood events in the stratigraphic record of the Waipaoa Shelf. Over the longer term, the sediment package preserved on the shelf and slope since the LGM can be explained in large measure by sequence-stratigraphic models forced by varying sea level and ongoing tectonic deformation of the margin. As sea level rose, sediment supply to the slope was reduced by about a factor of 5 due to shelf trapping. Despite this reduction, turbidites are found at similar frequency throughout the LGM-Present, as the dominant trigger appears to be subduction earthquakes, with large ones having a return interval of about 200 +/- 100 years. Sediment-budget exercises that consider both modern (river discharge versus centennial accumulation rates) and post-LGM (terrestrial production versus offshore isopachs) mass balances indicate that about half of the total sediment production from the Waipaoa escapes the study area. Moreover, a coupled sediment transport-hydrodynamic model and observations of textural trends on the shelf indicate that a large fraction of the sediment is carried outside the study area along the shelf to the northeast by the river plume or by combined current/wave activity. Therefore, we conclude that the WSS is an open system with sediment escape from the present day through the LGM.The organic matter associated with sediment as it moves from upland source to marine sink is a product of particle history, and provides a record of materials that have cycled over timescales of days to millions of years. The ubiquity of fossil Organic Carbon (OC) in both the terrestrial and marine realms of the Waipaoa attests both to the chronic nature of its source, crumbling mudstones further destabilized by land use, and its biogeochemical recalcitrance. Modern OC persists by virtue of its continual production along the S2S transit, and is buried and preserved within the adjacent marine depocenters. The Waipaoa contrasts with dispersal systems on wide, energetic shelves (e.g., the Amazon and Fly Rivers) where sediment is extensively refluxed in oxygenated overlying water resulting in the biogeochemical incineration of particulate OC. The Waipaoa, like other small mountainous rivers on active margins, exhibits a high riverine OC preservation efficiency (>50%) in its marine depocenters because of the relatively rapid, event-driven accumulation of sediment (C) 2015 Elsevier B.V. All rights reserved.

A fundamental goal of the Earth Science community is to understand how perturbations on Earth’s surface are preserved in the stratigraphic record. Recent Source to Sink (S2S) studies of the Waipaoa Sedimentary System (WSS) are synthesized herein to provide a holistic perspective of the processes that generate, transport and preserve sedimentary strata and organic carbon on the Waipaoa margin in the late Quaternary. Rapid uplift associated with subduction processes and weak sedimentary units have conspired to generate rapid rates of incision and erosion in the Waipaoa catchment since the Last Glacial Maximum (LGM). We show that although much of the sediment exported offshore during this time interval originated from valley excavation, a substantial portion emanated from hillslopes, mostly through deep-seated landslide and earthflow processes that were vigorous during periods of rapid fluvial incision just prior to the Pleistocene-Holocene transition. Lacustrine sediments deposited in naturally-dammed 7-kyold Lake Tutira provide a record of Holocene environmental controls on upper catchment sedimentation in the WSS. 1400 storms are identified, with one storm period (1830–2030 cal.

The head scarp of the Harper Hills landslide consists of ground cracks with vertical displacement and extension that opened during the 2010 Darfield (Canterbury) Mw 7.1 earthquake. The geomorphology of the cracks, regional geology and ground penetrating radar indicate that the landslide formed by bedding-controlled translation and joint-controlled toppling, and suggest incipient deep-seated movement. Crack depth and displacement along the head scarp vary along the ridge; maximum values are located where the head scarp is closest to the local ridge line. Increased seismic shaking due to topographic and geometric amplification of seismic waves is suggested as an explanation for this relationship. An excavation across the head scarp revealed no evidence of prior slip events over a time period that is likely to exceed the return period (1000–2500 years) of peak ground accelerations experienced at this location in the Darfield earthquake. We suggest that specific seismologic attributes of the Darfield earthquake may have influenced the location of landsliding in this instance. Studies of paleo-landslides must consider crack preservation potential as well as complex source/site effects that may complicate estimates of acceleration return periods from the subsurface investigation of individual landslide head scarps.

Quantifying how hillslopes respond to river incision and climate change is fundamental to understanding the evolution of uplifting landscapes during glacial-interglacial cycles. We investigated the interplay among uplift, river incision, and hillslope response in the nonglacial Waipaoa River catchment located in the exhumed inner forearc of an active subduction margin on the East Coast of the North Island of New Zealand. New high-resolution topographic data sets (light detection and ranging [lidar] and photogrammetry) combined with field mapping and tephrochronology indicate that hillslopes adjusted to rapid latest Pleistocene and Holocene river incision through the initiation and reactivation of deep-seated landslides. In the erodible marine sedimentary rocks of the Waipaoa sedimentary system, postincision deep-seated landslides can occupy over 30% of the surface area. The ages of tephra cover beds identified by electron microprobe analysis on 80 tephra samples from 173 soil test pits and 64 soil auger sites show that 4000-5000 yr after the initiation of river incision, widespread hillslope adjustment started between the deposition of the ca. 14,000 cal. yr B.P. Waiohau Tephra and the ca. 9420 cal. yr B.P. Rotoma Tephra. Tephrochronology and geomorphic mapping analysis indicate that river incision and deep-seated landslide slope adjustment were synchronous between main-stem rivers and headwater tributaries. Hillslope response in the catchment can include the entire slope, measured from river to ridgeline, and, in some cases, the interfluves between incising subcatchments have been dramatically modified through ridgeline retreat and/ or lowering. Using the results of our landform tephrochronology and geomorphic mapping, we derive a conceptual time series of hillslope response to uplift and climate change-induced river incision over the last glacial-interglacial cycle.

Hillslope response to climate-driven fluvial incision controls sediment export and relief generation in most mountainous settings. Following the shift to a warmer, wetter climate after the Last Glacial Maximum (LGM) (similar to 18 ka), the Waipaoa River (New Zealand) rapidly incised up to 120 meters, leaving perched, low-relief hillslopes unadjusted to that base level fall. In the Mangataikapua-a 16.5 km(2) tributary principally composed of weak melange-pervasive post-LGM landslides responded to >50 m of fluvial incision by sculpting and denuding >99% of the catchment. By reconstructing LGM and younger paleosurfaces from tephra identified by electron microprobe analysis (EMPA) and lidar-derived surface roughness, we estimate the volume, timing, and distribution of hillslope destabilization in the Mangataikapua and the relative contribution of landslide-prone terrain to post-LGM landscape evolution. We calculate volume change between four paleosurfaces constrained by tephra age (Rerewhakaaitu, 17.5 ka; Rotoma, 9.4 ka; Whakatane, 5.5 ka; and Waimihia, 3.4 ka). From the paleosurface reconstructions, we calculate the total post-LGM hillslope sediment contribution from the Mangataikapua catchment to be 0.5 +/- 0.06 (s.d.) km(3), which equates to a subcatchment averaged erosion rate of similar to 1.6 mm yr(-1). This is double the previous hillslope volume when normalized by study area, demonstrating that landslide-prone catchments disproportionately contribute to the terrestrial post-LGM sediment budget. Finally, we observe particularly rapid post-Waimihia erosion rates, likely impacted by human settlement.

Small river systems contribute a significant component of sediment delivered to oceans, but the temporal evolution of fluvially eroded landscapes is needed. A sequence of postglacial terraces in the unglaciated Waipaoa River catchment provides the opportunity to document fluvial incision and sediment flux on an ~2000-year timescale since the Last Glacial Maximum (LGM), which has previously only been undertaken for the entire post-LGM period. This study also calculates sediment mass, where previously sediment volume was calculated. Using a 15-m DEM, field mapping and surveying, and tephrochronology, we calculate rates of fluvial incision and sediment volumes excavated during successive age-constrained, postglacial, incision events and correlate these with a framework of inferred climatic events established for New Zealand. We identify seven periods of terrace formation each succeeded by a period of fluvial incision, six in total. Although the magnitude of the response during each incision event and thus the sediment volumes generated varied through time and across subcatchments draining two contrasting lithological terrains, we conclude that incision events were essentially synchronous, at least within the timeframe constrained by the ca. 2000year interval between successive eruptive airfall events. Slope relaxation processes were simultaneous with incision thereby indicating that both processes were likely climate driven. We identify a period of accelerated fluvial incision ~7mmy−1 commencing before ca. 14.0cal. ka BP (during the early postglacial period) and ceasing ca. 7.9cal. ka BP toward the end of the Early Holocene Warming period. The magnitude of this incision response was significantly higher in subcatchments draining highly erodible lithologies in the higher uplifting parts of the catchment when river bedload was at over capacity. In contrast, within the remainder of subcatchments draining the more resistant lithologies and in areas of lower uplift (and in parts subsiding), incision and sediment generation was moderated by the presence of knickpoints. Overall, since abandonment of the LGM to present day, fluvial incision in the Waipaoa and the adjacent Waimata catchments generated ~16.7km3 of sediment of which ~10km3 (~90% of the estimated 35Mt of glacial–postglacial slope and shelf sediment mass) was potentially available for transport offshore. Of this, 14.08km3 (7.4km3 derived from ‘upper’ and 6.7km3 from ‘remainder’ of subcatchments) was excavated from Waipaoa catchment at an average of ~0.6km3ka−1 of which ~80% was generated by ca. 7.9cal. ka BP. This potentially validates previous accounts of high rates of offshore sediment flux before 8000 14C YBP (ca. 8877cal. YBP). Thereafter, for the period mid-Holocene cooling and variability (MHCV) (ca. 6.5cal. ka BP) until the present day, the rate of incision across all subcatchments slowed to ~2mmy−1 and generated just ~20% of the total sediment volume. In part, this reflected a depletion of available sediment as rivers in the upper subcatchments returned to a steady state and, coincidental with an increase in accommodation space in the rapidly growing coastal floodplain, sediment flux to the marine depocentres was thereby limited.

Dextral slip at the western end of the east-west-striking Greendale fault during the 2010 M-W 7.1 Darfield earthquake transferred onto a northwest-trending segment, across an apparent transtensional zone, here named the Waterford releasing bend. We used detailed surface mapping, differential analysis of pre- and postearthquake light detection and ranging (LiDAR), and property boundary (cadastral) resurveying to produce high-resolution (centimeter-scale) estimates of coseismic ground-surface displacements across the indicate that the change in orientation on the Greendale fault incorporates elements of a large-scale releasing bend (from the viewpoint of westward motion on the south side of the fault) as well as a smaller-scale restraining stepover (from the viewpoint of southeastward motion on the north side of the fault). These factors result in the Water ford releasing bend exhibiting a decrease in displacement to near zero at the change in strike, and the presence within the overall releasing bend of a nested, localized restraining stepover with contractional bulging. The exceptional detail of surface deformation and kinematics obtained from this contemporary surface-rupture event illustrates the value of multimethod investigations. Our data provide insights into strike-slip fault bend kinematics, and into the potentially subtle but important structures that may be present at bends on historic and prehistoric rupture traces.

The September 2010 M-w 7.1 Darfield (Canterbury) earthquake in New Zealand is one of the best-recorded earthquakes of this magnitude. The earthquake occurred on a previously unidentified fault system and generated a 29.5 +/- 0.5-km-long surface rupture across a low-relief agricultural landscape. High-accuracy measurements of coseismic displacements were obtained at over 100 localities along the Greendale fault. Maximum net displacement (D-max) (5.3 +/- 0.5 m) and average net displacement (D-avg) (2.5 +/- 0.1 m) are anomalously large for an earthquake of this M-w.D-max/surface rupture length (SRL) and D-avg/SRL ratios are among the largest ever recorded for a continental strike-slip earthquake. "Geologically derived" estimates of moment magnitude (M-w(G)) are less than the seismologically derived M-w, derived using widely employed SRL-M-w scaling regressions. M-w(G) is greater than M-w using D-max- and D-avg-M-w regressions. The "geologically derived" static stress drop of 13.9 +/- 3.7 MPa provides a context with which to compare this earthquake rupture to interplate and intraplate ruptures of similar M-w. This data set provides fundamental information on fault rupture processes relevant to seismic-hazard modeling in this region and analogous settings globally.

Rupture of the Greendale Fault during the 4 September 2010, MW7.1 Darfield (Canterbury) earthquake produced a zone of ground-surface rupture that severely damaged several houses, buildings and lifelines. Immediately after the earthquake, surface rupture features were mapped in the field and from digital terrain models developed from airborne Light Detection and Ranging (lidar) data. To enable rebuild decisions to be made and for future land use planning, a fault avoidance zone was defined for the Greendale Fault following the Ministry for the Environment guidelines on 'Planning for the Development of Land on or Close to Active Faults'. We present here the most detailed map to date of the fault trace and describe how this was used to define and characterise the fault avoidance zone for land use planning purposes.