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David A. Johnston

Publications and source records attributed to David A. Johnston.

5 recordsLinked to original sources
USGS2024

A decade of shaking in the Garden City: The dynamics of preparedness, perceptions, and beliefs in Canterbury, New Zealand, and implications for earthquake information

This study explored earthquake preparedness over time - before, during, and 10 years after the Canterbury Earthquake Sequence (CES) in Aotearoa New Zealand (NZ). Surveys of Canterbury residents were conducted in 2009, 2013 and again in 2021, using variables derived from Community Engagement Theory (CET). The surveys measured earthquake perceptions and beliefs, participation and engagement, and preparedness actions. Results were compared across the three samples. Findings indicate that perceptions and beliefs (e.g. risk perception, outcome expectancy beliefs), and types of preparedness actions taken (e.g. collection of survival items, structural preparedness, community and agency relationships), differed over time, depending on people’s experiences before, during, and after the CES. For example, during and after the CES people were more likely to believe that preparing provided a benefit to daily life, but less likely to think it could reduce property damage, perhaps due to people’s experiences of disruption and damage during the earthquakes. An understanding of such dynamics can assist with the provision and timing of risk and preparedness information. This study highlights the importance of providing applicable and actionable preparedness information, that is relevant to people’s experiences, throughout an earthquake sequence. Such information might evolve and change in focus over time depending on risks and needs. Focus could also be given to information that builds peoples beliefs and capacities to undertake preparedness in evolving situations. Understanding preparedness in the context of different experiences and timeframes is useful in helping update models such as the CET, where the dynamics of time might be better incorporated.

Canterbury↗
USGS2020

Earthquake early warning in Aotearoa New Zealand: A survey of public perspectives to guide warning system development

Earthquake early warning (EEW) can be used to detect earthquakes and provide advanced notification of strong shaking, allowing pre-emptive actions to be taken that not only benefit infrastructure but reduce injuries and fatalities. Currently Aotearoa New Zealand does not have a nationwide EEW system, so a survey of the public was undertaken to understand whether EEW was considered useful and acceptable by the public, as well as perceptions of how and when such warnings should be communicated, before making an investment in such technology. We surveyed the public’s perspectives ( N = 3084) on the usefulness of EEW, preferred system attributes, and what people anticipated doing on receipt of a warning. We found strong support for EEW, for the purposes of being able to undertake actions to protect oneself and others (e.g. family, friends, and pets), and to mentally prepare for shaking. In terms of system attributes, respondents expressed a desire for being warned at a threshold of shaking intensity MM5–6. They suggested a preference for receiving a warning via mobile phone, supported by other channels. In addition to being warned about impending shaking, respondents wanted to receive messages that alerted them to other attributes of the earthquake (including the possibility of additional hazards such as tsunami), and what actions to take. People’s anticipated actions on receipt of a warning varied depending on the time available from the warning to arrival of shaking. People were more likely to undertake quicker and easier actions for shorter timeframes of <10 s (e.g., stop, mentally prepare, take protective action), and more likely to move to a nearby safe area, help others, look for more information, or take safety actions as timeframes increased. Given the public endorsement for EEW, information from this survey can be used to guide future development in Aotearoa New Zealand and internationally with respect to system attributes, sources, channels and messages, in ways that promote effective action.

Humanities & Social Sciences Communications↗
USGS2014

Variable population exposure and distributed travel speeds in least-cost tsunami evacuation modelling

Evacuation of the population from a tsunami hazard zone is vital to reduce life-loss due to inundation. Geospatial least-cost distance modelling provides one approach to assessing tsunami evacuation potential. Previous models have generally used two static exposure scenarios and fixed travel speeds to represent population movement. Some analyses have assumed immediate departure or a common evacuation departure time for all exposed population. Here, a method is proposed to incorporate time-variable exposure, distributed travel speeds, and uncertain evacuation departure time into an existing anisotropic least-cost path distance framework. The method is demonstrated for hypothetical local-source tsunami evacuation in Napier City, Hawke's Bay, New Zealand. There is significant diurnal variation in pedestrian evacuation potential at the suburb level, although the total number of people unable to evacuate is stable across all scenarios. Whilst some fixed travel speeds approximate a distributed speed approach, others may overestimate evacuation potential. The impact of evacuation departure time is a significant contributor to total evacuation time. This method improves least-cost modelling of evacuation dynamics for evacuation planning, casualty modelling, and development of emergency response training scenarios. However, it requires detailed exposure data, which may preclude its use in many situations.

Natural Hazards and Earth System Sciences↗
USGS1981

Guides to some volcanic terranes in Washington, Idaho, Oregon, and Northern California

This guidebook arose out of a series of field trips held in conjunction with the Pacific Northwest American Geophysical Union meeting held in Bend, Oregon, September 1979. The PNAGU meeting included special volcanology sessions planned by William I. Rose, Jr., Bruce A. Nolf, amd David A. Johnston. Publication of the guidebook volume was originally planned for early 1980 by the Oregon Department of Geology and Mineral Industries (DOGAMI). Inevitable delays, subsequent scheduling problems, and the death of Dave Johnston in the May 18 eruption of Mount St. Helens led to this publication as a USGS Circular. This circular differs from typical U.S. Geological Survey compilations in that not all these papers have been examined by the Geologic Names Committee of the Survey. This Committee is charged with ensuring consistent usage of formational and other stratigraphic names in U.S. Geological Survey publications. Because many of the contributions are from workers outside the Survey, review by the Geologic Names Committee would have been inappropriate. Each author provided camera-ready pages, and the articles have not been edited for uniformity of style or usage. The contributions are generally ordered so as to describe the areas from north to south. Typically, the roadlog comes after the descriptive article except in the case of the Medicine Lake Highland articles, for which the road log is first and several topical contributions follow.

California, Idaho, Oregon, Washington↗