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Jonathan W. Godt

Publications and source records attributed to Jonathan W. Godt.

At least 19 recordsLinked to original sources
USGS2026

Sackung at Bald Eagle ridge, central Colorado: An updated interpretation of ridge-spreading movement, structures, and mechanisms from 50 years (1975–2025) of U.S. Geological Survey research

Slow gravitational failures of mountain peaks and ridges are poorly understood. Herein, we report on 50 years of studies at a slowly spreading castellate ridge in the Sawatch Range in central Colorado. The orientations of geomorphic-structural features indicate that the fractured Precambrian granitic rock underlying the ridge has extended and spread northwestward toward the formerly glacier-covered Busk Creek valley. Results from surveying, field-based geomorphic-structural mapping using lidar, rock mass quality measurements, a passive seismic survey, and satellite radar provide a major update to research started by U.S. Geological Survey researchers in the 1970s and 1980s. New insights include a recognition that the entire ridge has slowly moved by concurrent sliding along an inferred northwest dipping, compound basal-slip surface (or zone), and through the formation of multiple grabens by normal faulting and flexural toppling along sets of pre-existing fractures that dip moderately (∼45°) to the southeast. We were unable to distinguish the presence of a sudden and strong contrast in seismic velocity across the inferred slip surface. Movement during the 50-year study period has been episodic and gradually decreasing, in correspondence with decreasing cumulative annual precipitation and increasing mean annual air temperatures. The fastest moving area, just upslope from the glacier trimline, had an average horizontal velocity of 3 – 4 mm/yr. Evidence suggests that movement started as a paraglacial response mechanism, but because of the site’s proximity to the Rio Grande Rift, we cannot exclude earthquake shaking as a mechanism for initiation or enhancement of slope movement. An estimate of longer-term horizontal movement from the exposed basal-slip surface at the uphill side of the ridgetop graben is ∼1.1 mm/yr for the 13 – 14 ky post-glacial period. Broad implications of our work are that: (1) long-term measurements (decades or longer) of slope movement can add insights into how sackungen form and evolve through time; (2) the identification of thrust faults and toes in zones of compression near valley bottoms can be crucial for interpreting sackung failure mechanisms, and (3) the use of passive-seismic techniques to identify the depth to a slip surface may not be successful in granitic terrain dominated by planar fractures and subtle changes in rock-mass characteristics.

Colorado↗
USGS2026

Building a national coordination structure to reduce and manage landslide risk in the United States

The National Landslide Hazard Reduction Program is a coordinated Federal effort to reduce landslide risks and losses in the United States. Created in 2021 by the National Landslide Preparedness Act (“the Act”), the Program aims to bolster national capacity to (a) assess landslide hazard and risk, (b) coordinate landslide risk reduction activities, (c) prepare and plan for landslide impacts, and (d) respond to landslide events. The U.S. Geological Survey (USGS) is the lead Federal agency for Program implementation. To support implementation, the Act establishes two new coordination bodies: (1) The Interagency Coordinating Committee on Landslide Hazards (ICCLH), with representation from the USGS, National Weather Service, National Science Foundation, Federal Emergency Management Agency, U.S. Forest Service, Department of Transportation, U.S. Army Corps of Engineers, and other Federal partners; and (2) the Federal Advisory Committee on Landslides (ACL), composed of external advisors from state, Tribal, territorial, and local geological and emergency management organizations, academic institutions, and the private sector. The ICCLH ensures coordination of resources and activities across the many Federal agencies whose missions include landslide hazard and risk. The ACL provides advice and guidance on Program implementation to the USGS and its Federal partners, supporting Program effectiveness, transparency, and accountability. Complementary to these two groups, the new USGS-led National Landslide Hazard and Risk Reduction Work Group brings together local and regional practitioners to share best practices and develop common approaches to landslide hazard and risk management. This presentation will detail USGS efforts over the past 5 years to build a multi-level, multi-sector coordination structure to facilitate landslide loss reduction at a national scale. We will reflect on challenges and opportunities, share examples of successful interagency collaborations, and highlight next steps for the U.S. National Landslide Hazard Reduction Program.

Conference Paper↗
USGS2026

USGS Landslide Disaster Assistance Team (LDAT): Reducing risk through international partnerships

The U.S. Geological Survey (USGS) Landslide Disaster Assistance Team (LDAT) collaborates with international counterparts to reduce landslide risk through technical training and emergency response. LDAT assists foreign partners, upon request, with developing landslide mapping, monitoring and response products and protocols. LDAT draws from USGS scientists and partners with countries globally. LDAT is currently engaging in a range of technical assistance activities in Chile, El Salvador, Fiji, the Federated States of Micronesia (FSM), Guatemala, Peru, and Sri Lanka. In this extended abstract, three examples of recent international landslide collaborations are showcased for FSM and with the Ministerio de Medio Ambiente y Recursos Naturales (MARN) in El Salvador, and the Mineral Resources Department (MRD) in Fiji. These efforts range from USGS- produced landslide initiation and runout maps (FSM) to feedback on independently led efforts to create national susceptibility maps (El Salvador), to trainings focused on building in-country landslide technical programs (Fiji). The LDAT partnerships help foreign partners reduce risk from landslides. The partnerships also help USGS scientists develop important international relationships that foster collaboration and broader understanding of landslides, which help advance the domestic USGS mission of reducing landslide risks.

Chuuk, Kosrae, Pohnpei↗
USGS2025

Preliminary field report of landslide hazards following Hurricane Helene

Executive Summary This report reflects our knowledge regarding the widespread landslide activity associated with Hurricane Helene observed during the U.S. Geological Survey’s (USGS) mission assignment to North Carolina in October 2024. The material in this report was originally prepared for the Federal Emergency Management Agency under mission assignment DR-4827-NC. The data and commentary in this report are reflective of a report provided to the Federal Emergency Management Agency (FEMA) on October 18, 2024, as well as information provided in briefings at the Buncombe County Emergency Operations Center. The report has been modified for public dissemination. This assessment was based on systematic visual examination and mapping of landslide locations from aerial and satellite imagery, visual and photographic observations from low-level helicopter overflights and conversations with local landslide experts from the North Carolina Geological Survey and Appalachian Landslide Consultants PLLC, and more than 50 years of combined landslide hazard professional experience of the mission-assigned field team. No systematic field investigations were done by the USGS. While responding to the event, the USGS did not identify any landslides that posed an immediate major threat to recovery personnel in parts of nine counties in North Carolina (Avery, Buncombe, Henderson, McDowell, Mitchell, Polk, Rutherford, Watauga, and Yancey); however, threats from renewed landslide activity may remain heightened in localized areas for months or even years. Known areas of the most abundant landslide occurrence include Bat Cave, Lake Lure, Chimney Rock, Swannanoa, Black Mountain, Fairview, steep areas in Asheville, and the Blue Ridge Parkway. The USGS shared detailed locations of known landslides with the Emergency Operations Centers. The thousands of landslide scars on hillsides and landslide deposits on flatter ground may present some threat to recovery activities. Soil and rocks will continue to erode from newly exposed landslide scars and may pose a threat to people and infrastructure who are immediately nearby. In general, the steeper and taller the landslide scar, the greater the potential threat. This threat is heightened during periods of rainfall and increases with the duration and intensity of rainstorms. Very heavy rainfall, or repeated rainfall events during short periods, could also initiate new landslides on steep slopes. Excavation of landslide deposits, particularly excavation of those deposits directly adjacent to steep slopes, may also pose a threat to nearby people and equipment. An interagency collaborative mapping effort led by the USGS that informed this assessment identified 1,155 landslide locations by the October 2024 briefings, but that number increased to 2,217 in a final reviewed version of the locations published in January 2025. Locations were mapped from satellite imagery, fixed-wing and helicopter surveys, media and social media, and field reports in the 3 weeks following the passage of the remnants of Hurricane Helene. USGS products outlined in this report are publicly available and include geotagged photographs from aerial reconnaissance, hazard models, an interactive view of mapped landslide locations, and landslide safety and education resources.

North Carolina, South Carolina, Tennessee, Virgini↗
USGS2022

National strategy for landslide loss reduction

Executive Summary Landslide hazards are present in all 50 States and most U.S. territories, and they affect lives, property, infrastructure, and the environment. Landslides are the downslope move­ment of earth materials under the force of gravity. They can occur without any obvious trigger. Widespread or severe land­slide events are often driven by such hazards as hurricanes, earthquakes, volcanic eruptions, heavy rain events, flooding, and wildfires. Landslides can also cause their own cascading consequences, such as the spread of hazardous materials or the creation of devastating local tsunamis. This strategy document describes goals and strategic actions of a comprehensive strategy to meet key challenges to reducing the Nation’s risk from landslide hazards equitably and effectively. The document follows the direction of the National Landslide Preparedness Act (Public Law 116–323) by presenting a strategy for addressing landslide hazards, including risk reduction and response. The act directs the Department of the Interior to establish a program that will work with State, Tribal, and local governments as well as with academia, the private sector, community-based groups, and nonprofit organizations to identify landslide hazards and risk and improve communication, coordination, and emergency preparedness, with the objective of reducing landslide losses. As the only Federal program dedicated to landslide hazard science, the U.S. Geological Survey’s Landslide Hazards Program will lead and coordinate many of the efforts described in this strategy document. Landslide hazard risk reduction must be undertaken collectively and collaboratively across the Federal Government. This strategy document will provide a framework for the creation of an interagency management plan that describes the programs, projects, workforce, and budgets required to carry out the national strategy. The strategy outlined in this document presents a vision of how to equitably produce, communicate, and apply landslide data and science to support a broad range of land management, infrastructure, planning, and emergency response decisions. These decisions are made by a variety of actors, including private and nonprofit landholders; State, Tribal, territorial, city, and county planners; emergency managers; engineers; infrastructure managers; Federal agencies and their partners; and community leaders and individuals. Supporting those decisions and reducing the Nation’s vulnerability to landslides requires overcoming three main challenges: (1) gaps in basic information needed to describe and understand landslide occurrence and societal risk, (2) difficulty in accurately mapping and forecasting landslide hazards, and (3) communication and coordination among the many jurisdictions and sectors that have responsi­bility for and interest in reducing landslide losses. To address those challenges, this strategy document puts forward a series of strategic actions to achieve four goals: Assess: Decision makers have access to detailed, nationwide, and contextually relevant information on land­slide hazard and risk. Coordinate: Landslide hazard mitigation, preparedness, response, and recovery efforts are coordinated across Federal, State, Tribal, territorial, and local levels. Plan: Communities and land managers are prepared and able to plan for landslide hazards. Respond: Landslide surveillance, warnings, and responses to events are effective, efficient, equitable, coopera­tive, and data-driven to protect lives, property, infrastructure, and the environment. These strategic actions focus on expanding the knowl­edge of societal risk posed by landslides as well as better understanding of where, when, and why they occur. They focus on applying that knowledge to support landslide risk reduction efforts and decisions, including the establishment of new advisory, coordination, and working groups focused on landslide hazard and risk. They take into account that supporting landslide loss reduction decisions also requires new guidance, tools, and training codeveloped with the entities, organizations, and individuals faced with making those decisions. Finally, they address actions needed to support and expand landslide warning information and improve the technical response to landslide emergencies.

Open-File Report↗
USGS2021

When hazard avoidance is not an option: Lessons learned from monitoring the postdisaster Oso landslide, USA

On 22 March 2014, a massive, catastrophic landslide occurred near Oso, Washington, USA, sweeping more than 1 km across the adjacent valley flats and killing 43 people. For the following 5 weeks, hundreds of workers engaged in an exhaustive search, rescue, and recovery effort directly in the landslide runout path. These workers could not avoid the risks posed by additional large-scale slope collapses. In an effort to ensure worker safety, multiple agencies cooperated to swiftly deploy a monitoring and alerting system consisting of sensors, automated data processing and web-based display, along with defined communication protocols and clear calls to action for emergency management and search personnel. Guided by the principle that an accelerating landslide poses a greater threat than a steadily moving or stationary mass, the system was designed to detect ground motion and vibration using complementary monitoring techniques. Near real-time information was provided by continuous GPS, seismometers/geophones, and extensometers. This information was augmented by repeat-assessment techniques such as terrestrial and aerial laser scanning and time-lapse photography. Fortunately, no major additional landsliding occurred. However, we did detect small headscarp failures as well as slow movement of the remaining landslide mass with the monitoring system. This was an exceptional response situation and the lessons learned are applicable to other landslide disaster crises. They underscore the need for cogent landslide expertise and ready-to-deploy monitoring equipment, the value of using redundant monitoring techniques with distinct goals, the benefit of clearly defined communication protocols, and the importance of continued research into forecasting landslide behavior to allow timely warning.

Washington↗
USGS2021

Evaluation of techniques for mitigating snowmelt infiltration-induced landsliding in a highway embankment

Infiltration-induced landslides threaten transportation infrastructure around the world, and impose both direct costs through repair and remediation work and indirect costs through lost economic activity. Therefore, finding the most cost-effective techniques to mitigate slope failures that can impact critical infrastructure links is desirable. The Straight Creek landslide, which affects a segment of Interstate 70 in Summit County, Colorado (USA), has experienced seasonal failure driven by rapid springtime snowmelt infiltration since the early 1970s, allowing changes in its stability to be studied. Past studies have established that seasonal failure is driven by pore-water pressure increase caused by the rapid infiltration of snowmelt and the hydraulic conductivity contrast between upper slope materials and the highway embankment. Two remediation designs have been applied to the site, including lightweight caissons beneath the highway surface in 2011 and 2012, and horizontal drains near the slide toe in 2012. The effects of the lightweight caissons and horizontal drains, as well as an alternative drain design that would extend into the hillslope above the highway embankment, are evaluated within a rigorous hydro-mechanical simulation framework along with a method to generate a field of local factor of safety. Model results show that the effect of the lightweight caissons on the factor of safety is no more than 1% during times of critical instability, as they do not affect the seasonal changes in hydrology that cause destabilizing decreases in effective stress along the failure surface. Horizontal drains are intended to reduce pore-water pressures, but the location of existing drains limit their efficacy due to the low hydraulic conductivity of subsurface materials underneath the highway. Model results indicate that these drains are only partially responsible for a reduction in movement rate since their installation, which is also due to lower annual cumulative snowmelt infiltration levels since 2012. Results also show that an alternative drain design could result in increased stability during critical periods by intercepting downslope subsurface flow before it arrives at the hydraulic conductivity contrast at the embankment.

Colorado↗
USGS2021

Principles for collaborative risk communication: Reducing landslide losses in Puerto Rico

Landslides are frequent and damaging natural hazards that threaten the people and the natural and built environments of Puerto Rico. In 2017, more than 70,000 landslides were triggered across the island by heavy rainfall from Hurricane María, prompting requests by local professionals for landslide education and outreach materials. This article describes a novel collaborative risk communication framework that was developed to meet those requests and shaped the creation of a Spanish- and English-language Landslide Guide for Residents of Puerto Rico. Collaborative risk communication is defined here as an iterative process guided by a set of principles for the interdisciplinary coproduction of hazards information and communication products by local and external stakeholders. The process that supports this form of risk communication involves mapping out the risk communication stakeholders in the at-risk or disaster-affected location—in this case Puerto Rico—and collaborating over time to address a shared challenge, such as landslide hazards. The approach described in this article involved the formation of a core team of government and university partners that expanded in membership to conduct collaborative work with an informal network of hazards professionals from diverse sectors in Puerto Rico. The following principles guided this process: cultural competence, ethical engagement, listening, inclusive decision making, empathy, convergence research, nested mentoring, adaptability, and reciprocity. This article contributes to the field of risk communication and emergency management by detailing these principles and the associated process in order to motivate collaborative risk communication efforts in different geographic and cultural contexts. While the work described here focuses on addressing landslides, the principles and process are transferable to other natural, technological, and willful human-caused hazards. They may also serve as a roadmap for future partnerships among government agencies and university researchers to inform the cocreation of science education and outreach tools.

Puerto Rico↗
USGS2020

Progress and lessons learned from responses to landslide disasters

Landslides have the incredible power to transform landscapes and also, tragically, to cause disastrous societal impacts. Whereas the mechanics and effects of many landslide disasters have been analyzed in detail, the means by which landslide experts respond to these events has garnered much less attention. Herein, we evaluate nine landslide response case histories conducted by the U.S. Geological Survey over the past two decades and summarize the event history, the response conducted, and the lessons learned from each event. We group the responses into three categories—providing event context from past events, addressing ongoing hazards, and acquiring data for the future—and present the nine case studies accordingly. We also summarize the progress in landslide response that has been made over the past two decades, including insights and advancements on the preparation for such events, the use of new technologies, and the importance of clear communication between all parties during disasters. We believe that exchanging and sharing experiences such as these will promote more clear and successful approaches for responses to landslide disasters in the future.

Book chapter↗
USGS2020

Landslides across the United States: Occurrence, susceptibility, and data limitations

Detailed information about landslide occurrence is the foundation for advancing process understanding, susceptibility mapping, and risk reduction. Despite the recent revolution in digital elevation data and remote sensing technologies, landslide mapping remains resource intensive. Consequently, a modern, comprehensive map of landslide occurrence across the United States (USA) has not been compiled. As a first step toward this goal, we present a national-scale compilation of existing, publicly available landslide inventories. This geodatabase can be downloaded in its entirety or viewed through an online, searchable map, with parsimonious attributes and direct links to the contributing sources with additional details. The mapped spatial pattern and concentration of landslides are consistent with prior characterization of susceptibility within the conterminous USA, with some notable exceptions on the West Coast. Although the database is evolving and known to be incomplete in many regions, it confirms that landslides do occur across the country, thus highlighting the importance of our national-scale assessment. The map illustrates regions where high-quality mapping has occurred and, in contrast, where additional resources could improve confidence in landslide characterization. For example, borders between states and other jurisdictions are quite apparent, indicating the variation in approaches to data collection by different agencies and disparity between the resources dedicated to landslide characterization. Further investigations are needed to better assess susceptibility and to determine whether regions with high relief and steep topography, but without mapped landslides, require further landslide inventory mapping. Overall, this map provides a new resource for accessing information about known landslides across the USA.

Landslides↗
USGS2019

Bayesian analysis of the impact of rainfall data product on simulated slope failure for North Carolina locations

In the past decades, many different approaches have been developed in the literature to quantify the load-carrying capacity and geotechnical stability (or the Factor of Safety, F_s) of variably saturated hillslopes. Much of this work has focused on a deterministic characterization of hillslope stability. Yet, simulated F_s values are subject to considerable uncertainty due to our inability to characterize accurately the soil mantle’s properties (hydraulic, geotechnical and geomorphologic) and spatiotemporal variability of the moisture content of the hillslope interior. This is particularly true at larger spatial scales. Thus, uncertainty-incorporating analyses of physically based models of rain-induced landslides are rare in the literature. Such landslide modeling is typically conducted at the hillslope scale using gauge-based rainfall forcing data with rather poor spatiotemporal coverage. For regional landslide modeling, the specific advantages and/or disadvantages of gauge-only, radar-merged and satellite-based rainfall products are not clearly established. Here, we compare and evaluate the performance of the Transient Rainfall Infiltration and Grid-based Regional Slope-stability analysis (TRIGRS) model for three different rainfall products using 112 observed landslides in the period between 2004 and 2011 from the North Carolina Geological Survey database. Our study includes the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis Version 7 (TMPA V7), the North American Land Data Assimilation System Phase 2 (NLDAS-2) analysis, and the reference ‘truth’ Stage IV precipitation. TRIGRS model performance was rather inferior with the use of literature values of the geotechnical parameters and soil hydraulic properties from ROSETTA using soil textural and bulk density data from SSURGO (Soil Survey Geographic database). The performance of TRIGRS improved considerably after Bayesian estimation of the parameters with the DiffeRential Evolution Adaptive Metropolis (DREAM) algorithm using Stage IV precipitation data. Hereto, we use a likelihood function that combines binary slope failure information from landslide event and ‘null’ periods using multivariate frequency distribution-based metrics such as the False Discovery and False Omission Rates. Our results demonstrate that the Stage IV-inferred TRIGRS parameter distributions generalize well to TMPA and NLDAS-2 precipitation data, particularly at sites with considerably larger TMPA and NLDAS-2 rainfall amounts during landslide events than null periods. TRIGRS model performance is then rather similar for all three rainfall products. At higher elevations, however, the TMPA and NLDAS-2 precipitation volumes are insufficient and their performance with the Stage IV-derived parameter distributions indicate their inability to accurately characterize hillslope stability.

North Carolina↗
USGS2019

Landslides triggered by Hurricane Maria: Assessment of an extreme event in Puerto Rico

Hurricane Maria hit the island of Puerto Rico on 20 September 2017 and triggered more than 40,000 landslides in at least three-fourths of Puerto Rico’s 78 municipalities. The number of landslides that occurred during this event was two orders of magnitude greater than those reported from previous hurricanes. Landslide source areas were commonly limited to surficial soils but also extended into underlying saprolite and bedrock. Slope failures occurred before, during, and after flooding, and many transitioned into long runout debris flows. Steep slopes in hilly and mountainous regions were particularly impacted by landslides due to antecedent soil moisture levels that were 11%–13% higher than average and rainfall totals of at least 250 mm within a 48 h period. High landslide densities were especially widespread across some geologic formations (e.g., granodiorite of the Utuado batholith); however, bedrock geology alone did not determine the location and distribution of landslides caused by Hurricane Maria. While rainfall data collected during Hurricane Maria were inconsistent, satellite-based soil moisture data were correlated with the distribution of landslides. In the future, the use of soil moisture data could enable assessments of regional landslide susceptibility prior to hurricanes or extreme precipitation events.

GSA Today↗
USGS2018

Science for a risky world—A U.S. Geological Survey plan for risk research and applications

Executive Summary Natural hazards—including earthquakes, tsunamis, volcanic eruptions, landslides, hurricanes, droughts, floods, wildfires, geomagnetic storms, and pandemics—can wreak havoc on human communities, the economy, and natural resources for years following an initial event. Hazards can claim lives and cause billions of dollars in damage to homes and infrastructure as well as lost or compromised economic activity and threats to national security. They also can have adverse environmental, social, economic, and health effects that extend well beyond the immediate area, sometimes with global implications. Changes in population growth, climate, and urbanization may exacerbate hazard impacts. Because of the potential severity of a single hazard event, reducing risk—the potential loss of societally important assets caused by these hazards—is a high priority for everyone, including policy makers, community members, emergency managers, resource managers, utility operators, business owners, and planners. These stakeholders demand usable, user-centric information to support decisions for planning a resilient future and for responding to and recovering from unanticipated events in more adaptable and cost-effective ways. Meeting this demand requires maximizing the use of environmental observations; hazards science; and research on communications, social stressors, and human behavior to deliver risk information in forms that are accessible by decision makers and the public alike. To achieve this, scientists and stakeholders must collaborate to match community needs with actionable insights, research, products, and tools, using advances in technology to improve information discovery and delivery.

Circular↗
USGS2018

Field and laboratory hydraulic characterization of landslide-prone soils in the Oregon Coast Range and implications for hydrologic simulation

Unsaturated zone flow processes are an important focus of landslide hazard estimation. Differences in soil hydraulic behavior between wetting and drying conditions (i.e., hydraulic hysteresis) may be important in landslide triggering. Hydraulic hysteresis can complicate soil hydraulic parameter estimates and impact prediction capability. This investigation focused on hydraulic property estimation for soil in a landslide‐prone area where the relative importance of hysteresis is unclear. Laboratory measurements of soil‐water retention from field soils in the Oregon Coast Range during wetting and drying show that pronounced hydraulic hysteresis is present. In contrast, a 4‐yr field data record of pore‐water pressure and soil‐water content from multiple soil pits at the same landslide‐prone area shows relatively minor hydraulic hysteresis compared with the laboratory estimates. Simulated subsurface hydrologic response parameterized using estimates from field data more closely matched hydrologic observations relative to model parameterization based on laboratory analysis of repacked soil samples. Our results suggest that (i) unsaturated hydraulic parameter estimates based on in situ field data, as opposed to laboratory measurements alone, may lead to more accurate simulation of the hydrologic response to rainfall, (ii) in situ data of soil‐water retention may need to include values at both high suctions and near saturation to improve estimates of soil hydraulic parameters for slope failure applications, and (iii) laboratory measurements of soil‐water retention made under dynamic conditions may overestimate hydraulic hysteresis.

Oregon↗
USGS2018

Overview of the geologic effects of the November 14, 2016, Mw 7.8 Kaikoura, New Zealand, earthquake

The November 14, 2016, Kaikoura, New Zealand, earthquake (moment magnitude [Mw] 7.8) triggered more than 10,000 landslides over an area of about 12,000 square kilometers in the northeastern part of the South Island of New Zealand. In collaboration with GNS Science (the Institute of Geological and Nuclear Science Limited), we conducted ground and helicopter reconnaissance of the affected areas and assisted in rapid hazard evaluation. The majority of the triggered landslides were shallow- to moderate-depth (1–10 meters), highly disrupted falls and slides in rock and debris from Lower Cretaceous graywacke sandstone in the Seaward Kaikoura Range. Deeper, more coherent landslides in weak Upper Cretaceous to Neogene sedimentary rock also were numerous in the gentler topography south and inland (west) of the Seaward Kaikoura Range. The principal ground-failure hazards from the earthquake were the hundreds of valley-blocking landslides, many of which impounded lakes and ponds that posed potential downstream flooding hazards. Both large and small landslides also blocked road and rail corridors in many locations, including the main north-south highway (State Highway 1), which was still closed in October 2017. As part of our investigation, we compared post-earthquake field observations to the output of models used to estimate near-real-time landslide probabilities following earthquakes. The models generally over-predicted landslide occurrence and thus need further refinement.

Kaikoura↗
USGS2018

Improving near‐real‐time coseismic landslide models: Lessons learned from the 2016 Kaikōura, New Zealand, earthquake

The U.S. Geological Survey (USGS) is developing near‐real‐time global earthquake‐triggered‐landslide products to augment the USGS Prompt Assessment of Global Earthquakes for Response (PAGER) system. The 14 November 2016 M w "> M w Mw 7.8 Kaikōura, New Zealand, earthquake provided a test case for evaluating the performance and near‐real‐time response applicability of three published global seismically induced landslide models. All three models obtain shaking estimates from the USGS ShakeMap, which is updated and sometimes changes significantly in the hours to days after an earthquake. The Kaikōura earthquake is a particularly valuable event that helps us better understand how changes to the ShakeMap affect the landslide models because the ShakeMap evolved significantly over several weeks as multifault rupture and seismic data were incorporated. We used the detailed landslide inventory available for this event for qualitative landslide model evaluation. We found that once a point source was replaced with an approximate rupture extent in ShakeMap, the landslide models were all successful at roughly identifying the area of highest hazard. This is notable, given that the models are relatively simple, coarse in resolution, and are based solely on input proxies that are globally available. However, all of the models dramatically overpredicted the hazard level, which indicates that improvements can be made. Subsequent updates to the ShakeMap resulted in improvements to model performance by some metrics and declining performance by others. In all cases, details of the ShakeMap strongly controlled the spatial pattern, even when those details were erroneous, such as the inclusion of a fault segment that did not rupture. If maps of landslide hazard are to be used effectively for rapid response, then we need to understand and clearly communicate the control that ShakeMap has over the models and how that typically evolves with time and is (or is not) reflected in reported uncertainties.

Bulletin of the Seismological Society of America↗
USGS2018

Landslides triggered by the 14 November 2016 Mw 7.8 Kaikōura Earthquake, New Zealand

The 14 November 2016 M w "> M w Mw 7.8 Kaikōura earthquake generated more than 10,000 landslides over a total area of about 10 , 000    km 2 "> 10 , 000 km 2 10,000 km2 , with the majority concentrated in a smaller area of about 3600    km 2 "> 3600 km 2 3600 km2 . The largest landslide triggered by the earthquake had an approximate volume of 20 ( ± 2 )    M   m 3 "> 20 ( ± 2 ) M m 3 20(±2) M m3 , with a runout distance of about 2.7 km, forming a dam on the Hapuku River. In this article, we present version 1.0 of the landslide inventory we have created for this event. We use the inventory presented in this article to identify and discuss some of the controls on the spatial distribution of landslides triggered by the Kaikōura earthquake. Our main findings are (1) the number of medium to large landslides (source area ≥ 10 , 000    m 2 "> ≥ 10 , 000 m 2 ≥10,000 m2 ) triggered by the Kaikōura earthquake is smaller than for similar‐sized landslides triggered by similar magnitude earthquakes in New Zealand; (2) seven of the largest eight landslides (from 5 to 20    M   m 3 "> 20 M m 3 20 M m3 ) occurred on faults that ruptured to the surface during the earthquake; (3) the average landslide density within 200 m of a mapped surface fault rupture is three times that at a distance of 2500 m or more from a mapped surface fault rupture; (4) the “distance to fault” predictor variable, when used as a proxy for ground‐motion intensity, and when combined with slope angle, geology, and elevation variables, has more power in predicting landslide probability than the modeled peak ground acceleration or peak ground velocity; and (5) for the same slope angles, the coastal slopes have landslide point densities that are an order of magnitude greater than those in similar materials on the inland slopes, but their source areas are significantly smaller.

Bulletin of the Seismological Society of America↗