22 research outputs found
Tsunami threat in the Indian Ocean from a future megathrust earthquake west of Sumatra
No full textAbstract not availableJohn McCloskey, Andrea Antonioli, Alessio Piatanesi, Kerry Sieh, Sandy Steacy, Suleyman Nalbant, Massimo Cocco, Carlo Giunchi, JianDong Huang, Paul Dunlo
A tale of two disasters: biases in risk communication
No full textTheme for 2016: Recognizing and representing eventsRisk communication, where scientists inform policy-makers
or the populace of the probability and magnitude of possible
disasters, is essential to disaster management – enabling
people to make better decisions regarding preventative steps,
evacuations, etc. Psychological research, however, has
identified multiple biases that can affect people’s
interpretation of probabilities and thus risk. For example,
availability (Tversky & Kahneman, 1973) is known to
confound probability estimates while the descriptionexperience
gap (D-E Gap) (Hertwig & Erev, 2009) shows low
probability events being over-weighted when described and
under-weighted when learnt from laboratory tasks. This paper
examines how probability descriptions interact with real
world experience of events. Responses from 294 participants
across 8 conditions showed that people’s responses, given the
same described probabilities and consequences, were altered
by their familiarity with the disaster (bushfire vs earthquake)
and its salience to them personally. The implications of this
for risk communication are discussed.Matthew B. Welsh, Sandy Steacy, Steve H. Begg, Daniel J. Navarr
Interseismic coupling, stress evolution, and earthquake slip on the Sunda megathrust
No full textThe extent to which interseismic coupling controls the slip distribution of large megathrust earthquakes is unclear, with some authors proposing that it is the primary control and others suggesting that stress changes from previous earthquakes are of first-order importance. Here, we develop a detailed stress history of the Sunda megathrust, modified by coupling, and compare the correlation between slip and stress with that of slip versus coupling. We find that the slip distributions of recent earthquakes are more consistent with the stress field than with the coupling distributions but observe that in places, the stress pattern is strongly dependent on poorly constrained values of slip in historical earthquakes. We also find that of the 13 earthquakes in our study for which we have hypocentral locations, only two appear to have nucleated in areas of negative stress, and these locations correspond to large uncertainties in the slip distribution of pre-instrumental events.Suleyman Nalbant, John McCloskey, Sandy Steacy, Mairead NicBhloscaidh, and Shane Murph
Tidal stress triggering of earthquakes in Southern California
No full textWe analyse the influence of the solid Earth tides and ocean loading on the occurrence time of Southern California earthquakes. For each earthquake, we calculate tidal Coulomb failure stress and stress rate on a fault plane that is assumed to be controlled by the orientation of the adjacent fault. To reduce bias when selecting data for testing the tide-earthquake relationship, we create four earthquake catalogues containing events within 1, 1.5, 2.5 and 5 km of nearest faults. We investigate the difference in seismicity rates at times of positive and negative tidal stresses/stress rates given three different cases. We consider seismicity rates during times of positive versus negative stress and stress rate, as well as 2 and 3 hr surrounding the local tidal stress extremes. We find that tidal influence on earthquake occurrence is found to be statistically non-random only in close proximity to tidal extremes meaning that magnitude of tidal stress plays an important role in tidal triggering. A non-random tidal signal is observed for the reverse events. Along with a significant increase in earthquake rates around tidal Coulomb stress maxima, the strength of tidal correlation is found to be closely related to the amplitude of the peak tidal Coulomb stress (τp). The most effective tidal triggering is found for τp ≥ 1 kPa, which is much smaller than thresholds suggested for static and dynamic triggering of aftershocks.Magda Bucholc and Sandy Steac
Indonesian earthquake: Earthquake risk from co-seismic stress
No full textFollowing the massive loss of life caused by the Sumatra-Andaman earthquake in Indonesia and its tsunami, the possibility of a triggered earthquake on the contiguous Sunda trench subduction zone is a real concern. We have calculated the distributions of co-seismic stress on this zone, as well as on the neighbouring, vertical strike-slip Sumatra fault, and find an increase in stress on both structures that significantly boosts the already considerable earthquake hazard posed by them. In particular, the increased potential for a large subduction-zone event in this region, with the concomitant risk of another tsunami, makes the need for a tsunami warning system in the Indian Ocean all the more urgent.John McCloskey, Suleyman S.Nalbant, Sandy Steac
Fault heterogeneity and earthquake scaling
No full textThere is an on-going debate in the seismological community as to whether stress drop is independent of earthquake size and this has important implications for earthquake physics. Here we investigate this question in a simple 2D cellular automaton that includes heterogeneity. We find that when the range of heterogeneity is low, the scaling approaches that of constant stress drop. However, clear deviations from the constant stress drop model are observed when the range of heterogeneity is large. Further, fractal distributions of strength show more significant departures from constant scaling than do random ones. Additionally, sub-sampling the data over limited magnitude ranges can give the appearance of constant stress drop even when the entire data set does not support this. Our results suggest that deviations from constant earthquake scaling are real and reflect the heterogeneity of natural fault zones, but may not provide much information about the physics of earthquakes
Camosun Showcase 2019: Professional, Scholarly & Creative Activity
No full textCamosun College values lifelong learning and faculty development. The faculty stories in this report highlight how the college enables development through scheduled development time, professional development funds, innovation and creativity grants and the supports provided by the Centre of Excellence for Teaching and Learning.Published in 2019 and released at the May 2, 2019 Walls Optional Conference. Faculty profiled in this report include: Corrine Michel & Dan Reeve; Applied Learning & Political Science Department.
Richard Burman, Applied Research.
Tommy Happynook, Indigenous Education & Community Connections.
Todd Ormiston, Indigenous Education & Community Connections.
Laura Hadwin, English Language Development Department.
John G. Boehme, Visual Arts Department.
Nicole Kilburn & Tara Tudor, Anthropology Department.
Ken Steacy & Joan Steacy, Communications Department, Comics & Graphic Novels.
Nancy Yakimoski, Visual Arts Department.
Carl Everitt, Tourism, Hospitality & Golf Management.
Elizabeth Morch, Dental Department, Dental Hygiene Program.
Sandra Carr, Fine Furniture/Joinery Program.
Dawn Smith, Centre for Excellence in Teaching & Learning (CETL).
Scott Kouri, Counselling Department.
Michael Borins, Mandy Hayre, & John Lee; Centre for Accessible Learning, Dental Hygiene Department, Chemistry and Geoscience Department
Elizabeth West, English Language Development Department, Centre for Excellence in Teaching & Learning
Messages from Sherri Bell, Camosun President and Sybil Harrison, Director of Learning Services are also featured. Cover art, "Blue on Black," by Nancy Yakimoski, Visual Arts Department
Ex-ante evaluation of tightening environmental policy: the case of mineral use in Dutch agriculture
No full textNon-point source pollution is notoriously difficult to asses. A relevant example is mineral emissions in the Netherlands. Since the mid 1980s the Dutch government has sought to reduce emissions through a wide variety of measures, the effect of which in turn is monitored using modeling techniques. This paper presents the current generation of mineral emission models from agriculture based on microsimulation of farms in combination with a spatial equilibrium model for the dispersion of manure from excess regions with high livestock intensities within the country to areas with low livestock intensities. The micro-simulation approach retains the richness in the heterogeneity of farm household decision making that are the core cause of the difficulty of assessing non-point source pollution, while using the best available data to track corresponding pollution. Using scenario analysis we are able to assess the possible effects of further tightening of agro-environmental policy.micro-simulation, spatial-equilibrium model, non-point source pollution, Environmental Economics and Policy,
Effects of source model variations on Coulomb stress analyses of a multi-fault intraplate earthquake sequence
No full textFault models are quickly produced and iteratively improved over weeks to years following a major earthquake, to characterise the dynamics of rupture, evaluate the role of stress transfer, and contribute to earthquake forecasting. We model Coulomb stress transfer (ΔCFS) between the largest foreshock (Mw 5.4; 1 year prior to first mainshock) and three Mw 6.1 to 6.5 earthquakes that occurred in a 12-hour period on January 22, 1988 in central Australia (Tennant Creek earthquake sequence) to investigate the role of static stress transfer in earthquake triggering relative to progressive source model development. The effects of fault model variance are studied using ΔCFS modelling of five different fault source model sequences (27 total models) using different inputs from seismic and geospatial data. Some initial models do not yield positive ΔCFS changes proximal to hypocentres but in all models, preceding earthquakes generate positive ΔCFS (≥0.1 bar) on ≥10 to 30% of the forthcoming receiver fault rupture areas. The most refined and data-integrative model reveals ΔCFS ≥ +0.7 to +13 bars within 2 km of impending hypocentres and large (≥30 to 99%) areas of positive ΔCFS. When compared to global compilations of threshold ΔCFS prior to impending ruptures (average = 3.71 bar, median = 1 bar), this suggests that Coulomb stress change theory adequately explains the Tennant Creek rupture sequence. In the most-refined model, earthquake inter-event times decrease as ΔCFS increases, suggesting that higher stress magnitudes may have more rapidly (within hours) triggered successive events, thus accounting for some temporal aspects of this sequence. ΔCFS analyses provide a useful framework for understanding the spatiotemporal aspects of some intraplate earthquakes. The progressive refinement of source models using emergent data may reduce epistemic uncertainties in the role of stress transfer that result from different model inputs, approaches, and results.Hiwa Mohammadi, Mark Quigley, Sandy Steacy, Brendan Duff
Stress transfer relations among the earthquakes that occurred in Kerman province, southern Iran since 1981
No full textWe explore the possible stress triggering relationship of the M >= 6.4 earthquakes that occurred in Kerman Province, southern Iran since 1981. We calculated stress changes due to both co-seismic sudden movement in the upper crust and the time-dependent viscous relaxation of the lower crust and/or upper mantle following the event. Four events of M >= 6.4 occurred between 1981 and 2005, on and close to the Gowk fault, show a clear Coulomb stress load to failure relationship. The 2003 M = 6.5 Bam earthquake, however, which occurred approximately 95 km SW of the closest Gowk event, shows a very weak stress relation to preceding earthquakes. The coseismic static stress change at the hypocentre of the Bam earthquake is quite small (similar to 0.006 bars). The time-dependent post-seismic stress change could be 26 times larger or 7 times lower than that of coseismic static stress alone depending on the choice of viscoelastic crustal model and the effective coefficient of friction. Given the uncertainties in the viscoelastic earth models and the effective coefficient of friction, we cannot confidently conclude that the 2003 Bam event was brought closer to failure through coseismic or post-seismic stress loading. Interestingly, the southern Gowk segment with a similar strike to that of the Bam fault, experienced a stress load of up to 8.3 bars between 1981 and 2003, and is yet to have a damaging earthquake
