School of Earth Sciences - Research Publications
Permanent URI for this collection
Search Results
1 - 10 of 18
-
ItemPhysical and Statistical Behavior of Multifault Earthquakes: Darfield Earthquake Case Study, New Zealand(AMER GEOPHYSICAL UNION, 2019-05)Abstract We use Coulomb stress change (CSC) analyses and seismicity data to model the physical and statistical behavior of the multifault source of the 4 September 2010 Mw 7.1 Darfield earthquake in New Zealand. Geodetic and seismologic data indicate this earthquake initiated on a severely misoriented reverse fault and propagated across a structurally complex fault network including optimally oriented faults. The observed rupture sequence is most successfully modeled if maximum CSC imposed by rupture of the hypocentral fault on to receiver faults exceeds theoretical threshold values of 1 to 5 MPa that are assigned based on fault slip tendency and stress drop analyses. CSC modeling using the same criteria but initiating the earthquake on other faults in the network results in a multifault rupture cascade for five of seven scenarios. Analysis of earthquake frequency‐magnitude distributions indicates that a Gutenberg‐Richter frequency‐magnitude distribution for the near‐source region cannot be rejected in favor of a characteristic earthquake distribution. However, characteristic behavior is more favored probabilistically because ruptures initiating on individual source faults in the system are statistically more likely to cascade into multifault ruptures with larger amalgamated Mw (Mwmax = 7.1) than to remain confined to the hypocentral source fault (Mw = 6.3 to 6.8). Our favored hypothesis is that system rupture behavior is regulated by misoriented faults that occupy critical geometric positions within the network, as previously proposed for the 2010 El Mayor‐Cucapah earthquake in Baja California. Other fault networks globally may exhibit similar physical and statistical behaviors.
-
ItemEffects of Earthquakes on Flood Hazards: A Case Study From Christchurch, New Zealand(MDPI, 2020-03)Earthquakes can influence flood hazards by altering the flux, volumes, and distributions of surface and/or subsurface waters and causing physical changes to natural and engineered environments (e.g., elevation, topographic relief, permeability) that affect surface and subsurface hydrologic regimes. This paper analyzes how earthquakes increased flood hazards in Christchurch, New Zealand, using empirical observations and seismological data. Between 4 September 2010 and 4 December 2017, this region hosted one moment magnitude (Mw) 7.1 earthquake, 3 earthquakes with Mw ≥ 6, and 31 earthquakes with local magnitude (ML) ≥ 5. Flooding related to liquefaction-induced groundwater pore-water fluid pressure perturbations and groundwater expulsion occurred in at least six earthquakes. Flooding related to shaking-induced ground deformations (e.g., subsidence) occurred in at least four earthquakes. Flooding related to tectonic deformations of the land surface (fault surface rupture and/or folding) occurred in at least two earthquakes. At least eight earthquakes caused damage to surface (e.g., buildings, bridges, roads) and subsurface (e.g., pipelines) infrastructure in areas of liquefaction and/or flooding. Severe liquefaction and associated groundwater-expulsion flooding in vulnerable sediments occurred at peak ground accelerations as low as 0.15 to 0.18 g (proportion of gravity). Expected return times of liquefaction-induced flooding in vulnerable sediments were estimated to be 100 to 500 years using the Christchurch seismic hazard curve, which is consistent with emerging evidence from paleo-liquefaction studies. Liquefaction-induced subsidence of 100 to 250 mm was estimated for 100-year peak ground acceleration return periods in parts of Christchurch.
-
ItemReply to 'Wiggle-match radiocarbon dating of the Taupo eruption'(NATURE PUBLISHING GROUP, 2019-10-11)
-
Item
-
ItemEvidence for magmatic carbon bias in 14C dating of the Taupo and other major eruptions(NATURE PUBLISHING GROUP, 2018-10-05)Prehistoric timescales, volcanic hazard assessment, and understanding of volcanogenic climate events rely on accurate dating of prehistoric eruptions. Most late Quaternary eruptions are dated by 14C measurements on material from close to the volcano that may be contaminated by geologic-sourced infinite-age carbon. Here we show that 14C ages for the Taupo (New Zealand) First Millennium eruption are geographically arrayed, with oldest ages closer to the vent. The current eruption wiggle match date of 232 ± 5 years CE is amongst the oldest. We present evidence that the older, vent-proximal 14C ages were biased by magmatic CO2 degassed from groundwater, and that the Taupo eruption occurred decades to two centuries after 232 CE. Our reinterpretation implies that ages for other proximally-dated, unobserved, eruptions may also be too old. Plateauing or declining tree ring cellulose δ13C and Δ14C values near a volcano indicate magmatic influence and may allow forecasting of super-eruptions.
-
ItemSlip rate estimation from tilting of marine terraces above an offshore listric thrust fault, Kaikoura, New Zealand(GNS Science, 2017-11-13)Slip on an offshore fault uplifted and tilted the Kaikoura Peninsula during the 2016 Kaikoura earthquake. Analysis of a 2012, 1m Lidar DEM shows that the uplifted Kaikoura marine terraces have been progressively tilted in the same manner since 120 ka. A Monte-Carlo analysis of tilt-age relationships, based on a model of listric faulting, and using published age data and Papuan and regional sea level curves, implies that slip rates have increased from 2.3 ± 1.3 mm/yr to 4.1 ± 1.2 mm/yr since c.60 ka. Comparison of the elevation of young, uplifted beaches surrounding the peninsula, with a Late Holocene sea level curve, suggests three earthquake events (including 2016) over 3 kyr. The timing of the earthquakes implies lower Late Holocene slip rates, compared with post-60 ka slip rates; comparison of these events with paleoseismic records of the Marlborough Fault System is interpreted to suggest latest Holocene clustering of seismicity.
-
ItemMélange versus forearc contributions to sedimentation and uplift, during rapid denudation of a young Banda forearc-continent collisional belt(Elsevier, 2017-05-01)New sedimentary geochemistry and petrographic analyses provide the most extensive sedimentary documentation yet of the rapid denudation of the young Timor orogen. The data from three basins including two widely-separated, well-dated sections of the Synorogenic Megasequence of Timor-Leste, and a re-dated DSDP 262, constrain the source and timing of detrital sediment flux during forearc-continent collision along the Timor sector of the Banda Arc. The exhumed synorogenic piggy-back basins formed above a mélange unit that developed at the expense of a weak stratigraphic horizon in the Mesozoic stratigraphy, and was exhumed to the sea floor in latest Messinian time. Following an interval of deep marine chalky marl sedimentation, an increasingly muddy sediment flux indicates that the island of Timor became emergent and shed sediment by 4.5 Ma. Comparison of exhumed sections with similar patterns in the DSDP262 chemistry suggests that the sediment source was probably located some 50-60 km distant from the basin, which is consistent with the Aileu region of Timor-Leste that shows an appropriate exhumation history. All sedimentation between 4.5 and 3.2 Ma was probably derived from a low-relief, rapidly eroding, and mudstone-dominated landscape with geochemical affinities to the Triassic-mudstone-derived synorogenic mélange. The mélange unit overlies and surrounds the Banda Terranc, and was presumably structurally emplaced by propagation of a decollement through the Triassic rocks during the collision. After 3.2 Ma, sedimentation was dominated by hard rock lithologies of the Banda Terrane, consisting of forearc cover and basement, the latter including elements of metamafic rocks and metapelites. This phase of sedimentation was accompanied by rapid uplift, which may have been partly driven by a transient imbalance between rock uplift and denudation as resistant lithologies emerged from below mélange-like mudstone. Previous work has suggested that the timing of collision in Timor-Leste and West Timor was substantially different. Our reevaluation of DSDP 262 facies migration history in the context of the re-dating presented here, favours a relatively synchronous onset of uplift in both halves of the island, but with different partitioning of strain between the foreland and hinterland in each half of the island.
-
ItemNo Preview AvailableSeismic hazards(Cambridge University Press, 2016-01-01)A textbook designed for students taking a course in Natural Hazards with an Australasian focus and context. Full colour and richly supported by photographs, illustrations and maps.
-
ItemGeophysical imaging of disrupted coastal dune stratigraphy and possible mechanisms, Haast, South Westland, New Zealand(TAYLOR & FRANCIS LTD, 2016-09)
-
ItemNo Preview AvailableMap of the 2010 Greendale Fault surface rupture, Canterbury, New Zealand: application to land use planning(TAYLOR & FRANCIS LTD, 2012)