Papers by Jennifer Eccles
AGU Fall Meeting Abstracts, Dec 1, 2016
AGU Fall Meeting Abstracts, Dec 1, 2019
EGU General Assembly Conference Abstracts, Apr 1, 2017
Agriculture as a Metaphor for Creativity in All Human Endeavors, 2018
Many parameter estimation problems are highly sensitive to errors. The Bayesian framework provide... more Many parameter estimation problems are highly sensitive to errors. The Bayesian framework provides a methodology for incorporating these errors into our inversion. However, how to characterise the errors in a way that can be efficiently utilised remains a problem in many inversions. Recently the Bayesian approximation error method has been utilised as a systematic way of characterising errors that arise from inaccuracies in the model. We describe the Bayesian approximation error method and demonstrate its use in a homogenisation example. In this example, it is shown that the coarse scale homogenised parameter can be estimated by accounting for the significant modelling error using the Bayesian approximation error method. This modelling error arises from inverting using a model that does not account for the fine scale and has a coarse finite element discretisation.
New Zealand Journal of Geology and Geophysics, 2020
Simulated spectral accelerations were inspected at three sites. For the M W 6.6 Wairoa N Ft earth... more Simulated spectral accelerations were inspected at three sites. For the M W 6.6 Wairoa N Ft earthquake, shaking had the potential to exceed design spectra at the CBD (shallow soils, 500 year return), airport (deep soils, 1000 year return) and Hūnua Ranges reservoirs (rock, 2500 year return for a safety evaluation earthquake). Dams that experienced similar shaking following the 2010 M w 8.8 Maule, Chile earthquake performed well with only minor slope failures, however land-sliding into the reservoir could pose a problem. Ground Motion Simulation of Hypothetical Earthquakes in the Upper North Island of New Zealand The upper North Island of New Zealand has large concentrations of population and infrastructure that make it vulnerable to earthquakes on the Kerepehi and Wairoa North faults. Using a physicsbased simulator, we modelled ground motions for M w 7.3 and M w 6.6 characteristic earthquakes on these structures. We considered the effects of low-velocity basins beneath the Hauraki Rift and the city of Hamilton that can amplify ground shaking. For a Kerepehi Fault earthquake, long period shaking was amplified a by factor of two to three in Hamilton and towns near the Firth of Thames. Severe to violent, long duration shaking would occur close to the source with the potential to trigger liquefaction that could damage flood defence networks and farmland in the Hauraki Plains. Auckland, Hamilton and Tauranga would experience moderate to very strong shaking. Impacts in Auckland are larger for a Wairoa North Fault earthquake, which could generate peak ground accelerations of 0.5 g at reservoir dams in the Hūnua Ranges, 0.2 g at the international airport, and 0.1 to 0.2 g at the CBD and port. Road, rail and transmission networks are vulnerable to disruption where they converge at infrastructure hotspots 10 km from the fault in South Auckland.
Geological Society of America Abstracts with Programs
Journal of Geophysical Research: Solid Earth, 2021
Although there were more recent ruptures of partial sections particularly in the North (Langridge... more Although there were more recent ruptures of partial sections particularly in the North (Langridge et al., 2021), the last large full section rupture took place in 1717. Thus, the Alpine Fault is late in its earthquake cycle. Howarth et al. (2021) estimate a 75% probability for a large earthquake (likely a full-section rupture with M W ≤ 8) in the central Alpine Fault section within the next 50 years.
Geophysical Research Letters, 2015
Fault Zone Guided Waves (FZGWs) have been observed for the first time within New Zealand's transp... more Fault Zone Guided Waves (FZGWs) have been observed for the first time within New Zealand's transpressional continental plate boundary, the Alpine Fault, which is late in its typical seismic cycle. Ongoing study of these phases provides the opportunity to monitor interseismic conditions in the fault zone. Distinctive dispersive seismic codas (~7-35 Hz) have been recorded on shallow borehole seismometers installed within 20 m of the principal slip zone. Near the central Alpine Fault, known for low background seismicity, FZGW-generating microseismic events are located beyond the catchment-scale partitioning of the fault indicating lateral connectivity of the low-velocity zone immediately below the near-surface segmentation. Initial modeling of the low-velocity zone indicates a waveguide width of 60-200 m with a 10-40% reduction in S wave velocity, similar to that inferred for the fault core of other mature plate boundary faults such as the San Andreas and North Anatolian Faults. The Alpine Fault has not ruptured historically; however, paleoseismicity on the southern portion of the Alpine Fault reveals a pattern of 24 large events with an average recurrence time of 329 ± 68 years [Berryman et al., 2012]. The last large (> M8) earthquake on the central Alpine Fault occurred in 1717 A.D. [Wells et al., 1999], and hence, the Alpine Fault is considered to be late in its seismic cycle. The central Alpine Fault is a region of anomalously low background microseismicity [Boese et al., 2012; Bourguignon et al., 2015]. The spatial variations in current seismicity observed in the central Southern Alps and localized seismic tremor and low-frequency earthquakes are indicative of variable fluid and stress conditions near the fault [
Journal of Geophysical Research: Solid Earth, 2020
The New Zealand Alpine Fault is a major plate boundary that is expected to be close to rupture, a... more The New Zealand Alpine Fault is a major plate boundary that is expected to be close to rupture, allowing a unique study of fault properties prior to a future earthquake. Here we present 3-D seismic data from the DFDP-2 drill site in Whataroa to constrain valley structures that were obscured in previous 2-D seismic data. The new data consist of a 3-D extended vertical seismic profiling (VSP) survey using three-component and fiber optic receivers in the DFDP-2B borehole and a variety of receivers deployed at the surface. The data set enables us to derive a detailed 3-D P wave velocity model by first-arrival traveltime tomography. We identify a 100-460 m thick sediment layer (mean velocity 2,200 ± 400 m/s) above the basement (mean velocity 4,200 ± 500 m/s). Particularly on the western valley side, a region of high velocities rises steeply to the surface and mimics the topography. We interpret this to be the infilled flank of the glacial valley that has been eroded into the basement. In general, the 3-D structures revealed by the velocity model on the hanging wall of the Alpine Fault correlate well with the surface topography and borehole findings. As a reliable velocity model is not only valuable in itself but also crucial for static corrections and migration algorithms, the Whataroa Valley P wave velocity model we have derived will be of great importance for ongoing seismic imaging. Our results highlight the importance of 3-D seismic data for investigating glacial valley structures in general and the Alpine Fault and adjacent structures in particular. Viewed on a regional scale, the central Alpine Fault appears as a straight boundary (e.g., Norris & Cooper, 2001; Sutherland et al., 2006). Crustal-scale seismic reflection data show a single oblique fault striking northeastward and dipping 40−60 • to the southeast at depths of 15-30 km (e.g.,
68th EAGE Conference and Exhibition incorporating SPE EUROPEC 2006, 2006
Summary The iSIMM project has demonstrated the effectiveness of low-frequency acquisition in coun... more Summary The iSIMM project has demonstrated the effectiveness of low-frequency acquisition in countering the loss due to scattering by the high-impedance contrasts and rough surfaces presented by stacked basalt flows (Spitzer et al., 2005). Both the oceanbottom seismometer (OBS) profiles and the densely sampled towed-streamer profiles in the iSIMM surveys allowed comparison of deep -towed, peak-tuned, and bubbletuned airgun sources. Supported by earlier analysis (Lunnon et al., 2003), we find source tow depth has greater impact upon bandwidth than does tuning mode, although, for the configurations tested, the bubble-tuned source produced a more compact signature. Shot-by-shot signature deconvolution was successfully applied to bubble-tuned streamer data in s ub-critical regimes, but wide-angle signatures were adversely affected by standard deconvolution. This paper evaluates the performance of the peak- and bubble-tuned sources and presents a robust shaping deconvolution.
Geophysical Journal International, 2017
We develop a computationally efficient approach to compute the waveforms and the dispersion curve... more We develop a computationally efficient approach to compute the waveforms and the dispersion curves for fault-zone trapped waves guided by arbitrary transversely isotropic across-fault velocity models. The approach is based on a Green's function type representation for F L and F R type fault-zone trapped waves. The model can be used for simulation of the waveforms generated by both infinite line sources (2-D) and point sources (3-D). The numerical scheme is based on a high order finite element approximation and, to increase computational efficiency, we make use of absorbing boundary conditions and mass lumping of finite element matrices.
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Papers by Jennifer Eccles