ORCID Profile
0000-0001-9947-3710
Current Organisations
University of Birmingham
,
Jet Propulsion Laboratory
,
Delft University of Technology
,
California Institute of Technology
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Publisher: SPIE
Date: 12-07-2018
DOI: 10.1117/12.2313968
Publisher: New Zealand Society for Earthquake Engineering
Date: 30-06-2017
DOI: 10.5459/BNZSEE.50.2.106-116
Abstract: Tens of thousands of landslides were generated over 10,000 km2 of North Canterbury and Marlborough as a consequence of the 14 November 2016, Mw7.8 Kaikōura Earthquake. The most intense landslide damage was concentrated in 3500 km2 around the areas of fault rupture. Given the sparsely populated area affected by landslides, only a few homes were impacted and there were no recorded deaths due to landslides. Landslides caused major disruption with all road and rail links with Kaikōura being severed. The landslides affecting State Highway 1 (the main road link in the South Island of New Zealand) and the South Island main trunk railway extended from Ward in Marlborough all the way to the south of Oaro in North Canterbury. The majority of landslides occurred in two geological and geotechnically distinct materials reflective of the dominant rock types in the affected area. In the Neogene sedimentary rocks (sandstones, limestones and siltstones) of the Hurunui District, North Canterbury and around Cape C bell in Marlborough, first-time and reactivated rock-slides and rock-block slides were the dominant landslide type. These rocks also tend to have rock material strength values in the range of 5-20 MPa. In the Torlesse ‘basement’ rocks (greywacke sandstones and argillite) of the Kaikōura Ranges, first-time rock and debris avalanches were the dominant landslide type. These rocks tend to have material strength values in the range of 20-50 MPa. A feature of this earthquake is the large number (more than 200) of valley blocking landslides it generated. This was partly due to the steep and confined slopes in the area and the widely distributed strong ground shaking. The largest landslide dam has an approximate volume of 12(±2) M m3 and the debris from this travelled about 2.7 km2 downslope where it formed a dam blocking the Hapuku River. The long-term stability of cracked slopes and landslide dams from future strong earthquakes and large rainstorms are an ongoing concern to central and local government agencies responsible for rebuilding homes and infrastructure. A particular concern is the potential for debris floods to affect downstream assets and infrastructure should some of the landslide dams breach catastrophically. At least twenty-one faults ruptured to the ground surface or sea floor, with these surface ruptures extending from the Emu Plain in North Canterbury to offshore of Cape C bell in Marlborough. The mapped landslide distribution reflects the complexity of the earthquake rupture. Landslides are distributed across a broad area of intense ground shaking reflective of the elongate area affected by fault rupture, and are not clustered around the earthquake epicentre. The largest landslides triggered by the earthquake are located either on or adjacent to faults that ruptured to the ground surface. Surface faults may provide a plane of weakness or hydrological discontinuity and adversely oriented surface faults may be indicative of the location of future large landslides. Their location appears to have a strong structural geological control. Initial results from our landslide investigations suggest predictive models relying only on ground-shaking estimates underestimate the number and size of the largest landslides that occurred.
Publisher: Oxford University Press (OUP)
Date: 11-08-2022
Abstract: Relativistic jets are believed to have a substantial impact on the gas dynamics and evolution of the interstellar medium (ISM) of their host galaxies. In this paper, we aim to draw a link between the simulations and the observable signatures of jet-ISM interactions by analyzing the emission morphology and gas kinematics resulting from jet-induced shocks in simulated disc and spherical systems. We find that the jet-induced laterally expanding forward shock of the energy bubble sweeping through the ISM causes large-scale outflows, creating shocked emission and high-velocity dispersion in the entire nuclear regions (∼2 kpcs) of their hosts. The jetted systems exhibit larger velocity widths (& km s−1), broader Position-Velocity maps and distorted symmetry in the disc’s projected velocities than systems without a jet. We also investigate the above quantities at different inclination angles of the observer with respect to the galaxy. Jets inclined to the gas disc of its host are found to be confined for longer times, and consequently couple more strongly with the disc gas. This results in prominent shocked emission and high-velocity widths, not only along the jet’s path, but also in the regions perpendicular to them. Strong interaction of the jet with a gas disc can also distort its morphology. However, after the jets escape their initial confinement, the jet-disc coupling is weakened, thereby lowering the shocked emission and velocity widths.
Publisher: SPIE
Date: 10-07-2018
DOI: 10.1117/12.2311686
Publisher: American Geophysical Union (AGU)
Date: 2022
DOI: 10.1029/2021JB021997
Abstract: Although submarine landslides have been studied for decades, a persistent challenge is the integration of erse geoscientific datasets to characterize failure processes. We present a core‐log‐seismic integration study of the Tuaheni Landslide Complex to investigate intact sediments beneath the undeformed seafloor as well as post‐failure landslide deposits. Beneath the undeformed seafloor are coherent reflections underlain by a weakly‐reflective and chaotic seismic unit. This chaotic unit is characterized by variable shear strength that correlates with density fluctuations. The basal shear zone of the Tuaheni landslide likely exploited one (or more) of the low shear strength intervals. Within the landslide deposits is a widespread “Intra‐debris Reflector”, previously interpreted as the landslide's basal shear zone. This reflector is a subtle impedance drop around the boundary between upper and lower landslide units. However, there is no pronounced shear strength change across this horizon. Rather, there is a pronounced reduction in shear strength ∼10–15 m above the Intra‐debris Reflector that presumably represents an induced weak layer that developed during failure. Free gas accumulates beneath some regions of the landslide and is widespread deeper in the sedimentary sequence, suggesting that free gas may have played a role in pre‐conditioning the slope to failure. Additional pre‐conditioning or failure triggers could have been seismic shaking and associated transient fluid pressure. Our study underscores the importance of detailed core‐log‐seismic integration approaches for investigating basal shear zone development in submarine landslides.
Publisher: Springer Science and Business Media LLC
Date: 13-02-2020
Publisher: Oxford University Press (OUP)
Date: 28-01-2022
Abstract: We use the results of relativistic hydrodynamic simulations of jet-interstellar medium (ISM) interactions in a galaxy with a radio-loud AGN to quantify the extent of ionization in the central few kpcs of the gaseous galactic disc. We perform post-process radiative transfer of AGN radiation through the simulated gaseous jet-perturbed disc to estimate the extent of photo-ionization by the AGN with an incident luminosity of 1045 erg s−1. We also map the gas that is collisionally ionized due to shocks driven by the jet. The analysis was carried out for simulations with similar jet power (1045 erg s−1) but different jet orientations with respect to the gas disc. We find that the shocks from the jets can ionize a significant fraction (up to 33 ${{\\ \\rm per\\ cent}}$) of dense gas ($n\\gt 100\\, \\mathrm{cm^{-3}}$) in the disc, and that the jets clear out the central regions of gas for AGN radiation to penetrate to larger distances in the disc. Jets inclined towards the disc plane couple more strongly with the ISM and ionize a larger fraction of gas in the disc as compared to the vertical jet. However, similar to previous studies, we find that the AGN radiation is quickly absorbed by the outer layers of dense clouds in the disc, and is not able to substantially ionize the disc on a global scale. Thus, compared to jet–ISM interactions, we expect that photo-ionization by the AGN radiation only weakly affects the star-formation activity in the central regions of the galactic disc (≲ 1 kpc), although the jet-induced shocks can spread farther out.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United States of America
Start Date: 2017
End Date: 2020
Funder: Marsden Fund
View Funded Activity