Michelle Salmon

• PhD Geophysics
• Australian National University

The evolution of fault strength and behavior during the initial stages of slip plays an important role in driving the onset of instability and fault weakening. Using small-displacement triaxial experiments on quartz sandstone, this study highlights the rapid onset of microstructural change on fault interfaces and identifies new evidence for an evol...

Current estimates of Moho depth in southeastern Australia are based on sparse sampling. The results are augmented with 180 new Moho estimates constructed from spatial stacks of crustal P wave reflectivity derived from autocorrelograms at over 750 stations. The spatial stacks of reflectivity are constructed using a Gaussian with half-width 0.5°. Pic...

We use teleseismic body wave tomography to reveal anomalous P wave velocity variations in the upper mantle beneath south-east Australia. Data are sourced from the WOMBAT transportable seismic array, the largest of its kind in the southern hemisphere, which enables horizontal resolution of approximately 50 km to be achieved over a large region that...

INTRODUCTION Astronomy has space travel and supernovas, chemistry has goo and explosions, biology has creepy-crawlies and medical miracles, and the earth sciences have earthquakes and volca-noes. Each of the sciences has some way to engage and inspire the future generations of scientists. As researchers we are con-stantly seeking ways to communicat...

We use ambient noise recordings from the largest transportable seismic array in the Southern Hemisphere to image azimuthal variations in Rayleigh wave phase anisotropy in the crust beneath southeast Australia. This region incorporates a transition from the Precambrian shield region of Australia in the west to younger Phanerozoic terranes in the eas...

The Phanerozoic Tasmanides of eastern Australia is comprised of a series of orogenic belts that developed along the east margin of Gondwana following the breakup of the supercontinent Rodinia and subsequent formation of the Pacific Ocean. The tectonic complexities of this region have been well studied, but most work has been confined to evidence co...

In general, seismic methods provide a reliable way to image the crust–mantle interface, which is marked by a rapid increase in seismic velocity (the Moho). However, the coverage provided by seismic networks is necessarily limited due to access difficulties, and the cost and labour involved in collecting data. Gravity data provide an alternative way...

Ambient seismic noise data from the ongoing WOMBAT transportable seismic array in southeast Australia, the largest deployment of its kind in the Southern Hemisphere, are used to produce a high-resolution 3-D shear wave velocity model of the region. We apply a two-stage, transdimensional, hierarchical Bayesian inversion approach to recover phase vel...

A 581 km vibroseis-source, deep seismic reflection survey was acquired through the Capricorn Orogen of Western Australia and, for the first time, provides an unprecedented view of the deep crustal architecture of the West Australian Craton. The survey has imaged three principal suture zones, as well as several other lithospheric-scale faults. The s...

The Australian Seismometers in Schools program (AuSIS) has just completed year one of its initial four-year program. The year has been filled with excitement as we completed installing pilot instruments in schools, launched the program nationally and received over 110 "Expressions of Interest" from schools around Australia. The data quality has exc...

Lithospheres of different thicknesses are often juxtaposed by movement on a continental-transform boundary. Such a boundary with a step change in densities may trigger a gravitational instability as lateral pressure gradients are created where normal mantle lithosphere terminates against less dense asthenospheric mantle. Here we show, for plausible...

Although Australia has been the subject of a wide range of seismological studies, these have concentrated on specific features of the continent at crustal scales and on the broad scale features in the mantle. The Australian Seismological Reference Model (AuSREM) is designed to bring together the existing information, and provide a synthesis in the...

Although Australia has been the subject of a wide range of seismological studies, these have concentrated on specific features of the continent at crustal scales and on the broad scale features in the mantle. The Australian Seismological Reference Model (AuSREM) is designed to bring together the existing information, and provide a synthesis in the...

Interpolation of spatial data is a widely used technique across the Earth sciences. For example, the thickness of the crust can be estimated by different active and passive seismic source surveys, and seismologists reconstruct the topography of the Moho by interpolating these different estimates. Although much research has been done on improving th...

The lithosphere beneath eastern Australia was formed during a protracted period of Palaeozoic orogeny that began in the Early Cambrian and terminated in the Middle Triassic. Accretion of new and reworked lithosphere occurred outboard of the proto-Pacific margin of Gondwana, which at that time extended some 20,000 km along the east margin of Precamb...

Seismic data coverage of Australia has greatly increased over the last 10 years, providing an opportunity to update the seismological model of the continent. Good seismological models of the Earth's crust and upper mantle are critical for many tasks, such as the calculation of earthquake source parameters, regional hazard modelling and imaging of l...

Since 2004 more than 7000 km of full-crustal reflection profiles have been collected across Australia to give a total of more than 11 000 km, providing valuable new constraints on crustal structure. A further set of hitherto unexploited results comes from 150 receiver functions distributed across the continent, mostly from portable receiver sites....

Receiver function analysis reveals a 7 km step-like change in crustal thickness across the Taranaki–Ruapehu Line (TR-line) of North Island, New Zealand. The TR-line runs east–west between the active andesite volcanoes of Mt Taranaki and Ruapehu and marks the southern-most extent of subduction zone volcanism in New Zealand. North of the TR-line rece...

At many active continental margins of the world there exist geophysical data that could be interpreted either in terms of a slab break off, or the loss of thickened mantle lithosphere from the overriding plate. Here we examine central Western North Island of New Zealand, where a particular good geological and geophysical data base permits a test be...

Two geophysical features characterise the anomalous crust–mantle structure beneath central North Island of New Zealand: the apparent thinning of the felsic crust by a factor of at least 50%, and upper mantle P-wave velocities (Pn phase) about 10% less than normal (∼ 7.3–7.4 km/s). Pn velocities increase slowly to a maximum of ∼ 7.8 km/s at a depth...

We present a new crustal thickness map of Australia estimated from the compilation of seismic receiver functions, seismic reflection and refraction profiles. This map represents the current status of the AusMoho project, which ultimately aims to image the Australian continental crust with a 50 km resolution. The current Moho map includes over 250 d...

In central North Island a useful geological and geophysical data exists to examine the evolution from retro-arc compression to back-arc extension in the Neogene. We show that the switch from compression to extensional deformation is related in space and time with an event that rapidly removed much of the mantle lithosphere beneath central and weste...

The North Island of New Zealand lies on the Australian Plate, above the subducted Pacific Plate. The highest point on the North Island is near its centre on Mt. Ruapehu Volcano, which is the southernmost in a line of active volcanoes associated with extension in the Taupo Volcanic Zone, the southern limit of the Lau-Havre Trough. South of Mt. Ruape...

Back-arc extension and spreading has been splitting apart the central North Island of New Zealand since the Pliocene. But the impressive volcanism and geothermal activity linked to this extension belies the extensive period of compression, and thrusting that dominated the pre-Pliocene tectonics of the central North Island. Up to 100 km of Oligocene...

Central North Island, New Zealand, provides an unusually complete geological and geophysical record of the onset and evolution of subduction at a continental margin. Whereas most subduction zones are innately two-dimensional, North Island of New Zealand displays a distinct three-dimensional character in the back-arc regions. Specifically, we observ...

Thickening of continental lithosphere followed by its convective removal provides a mechanism to explain a broad range of surface observations from the formation of deep sedimentary basins to uplift on a scale similar to that seen at hot spots. In New Zealand we see both geological and geophysical evidence for the convective removal of the lower li...

Back-arc basins of the western Pacific are elevated some 1-2 km above the adjacent oceanic floor. Where oceanic back-arc basins propagate into continental lithosphere we also see an uplift signal, which can be mapped and evaluated with geological methods. Trying to understand the driving force for this uplift requires seismological methods to quant...

We use crustal structure and exhumation data to estimate the density and partial melt variation in the mantle wedge of a back-arc extension system. A program of explosion seismology (NIGHT) in the central North Island (CNI) of New Zealand has unearthed an intriguing, isostatic contradiction: an association of profoundly thin continental crust with...

We use seismic attenuation and magnetotelluric data to determine the nature and location of a boundary that marks the transition from extension to compression, North Island New Zealand. This boundary, termed the Taranaki-Ruapehu Line (TRL), has long been recognised as a fundamental boundary between lithosphere of contrasting nature. Geophysical evi...

Back-arc extension occurs within the continental lithosphere of North Island, New Zealand, resulting in normal faulting, geothermal activity, active volcanism and geodetically determined extension at a rate of about 10 mm/y. Coeval with the development of volcanism was the growth of a topographic dome that is 400 km in width and, on the basis of ex...

Three geophysical techniques have been used to investigate the location and the nature of a large-scale change in crust and uppermost mantle properties below the western North Island of New Zealand. Receiver function analysis reveals a step like change in crustal thickness from ~ 25 km below the northwestern North Island to ≥ 32 km in the southwest...