Preprints
Filtering by Subject: Geophysics and Seismology
Large-scale crustal structure beneath Singapore using receiver functions from a dense urban nodal array
Published: 2020-02-20
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Geophysics has a role to play in the development of smart cities, for example through geohazard mitigation and subsurface imaging for underground construction. This is particularly true for Singapore, one of the worlds most densely populated countries. Imaging of Singapores subsurface is required to identify geological faults, model shaking from future earthquakes and provide a framework for [...]
Connecting a broad spectrum of transient slip on the San Andreas fault
Published: 2020-02-13
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Strain accumulated on the deep extension of some faults are episodically released during transient slow-slip events which can subsequently load the shallow seismogenic region. At the San Andreas fault, the characteristics of slow-slip events are difficult to constrain geodetically due to their small deformation signal. Slow-slip events are often accompanied by coincident tremor bursts composed of [...]
Constraints on mantle viscosity and Laurentide ice sheet evolution from pluvial paleolake shorelines in the western United States
Published: 2020-02-12
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Physical Sciences and Mathematics
The deformation pattern of the paleoshorelines of extinct Lake Bonneville were among the first features to indicate that Earths interior responds viscoelastically to changes in surface loads (Gilbert, 1885). Here we revisit and extend this classic study of isostatic rebound with updated lake chronologies for Lake Bonneville and Lake Lahontan as well as revised elevation datasets of shoreline [...]
History of on-board equipment improvement for GNSS-A observation with focus on observation frequency
Published: 2020-02-12
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
The Global Navigation Satellite System-Acoustic ranging combination technique (GNSS-A) is a seafloor geodetic technique that enables precise global seafloor positioning to detect subseafloor geophysical phenomena. The technique requires a sea surface observation platform that combines GNSS positioning and acoustic ranging. Currently, a survey vessel is used as the platform, which entails [...]
The 2019 MW 5.7 Changning earthquake, Sichuan Basin, China – a shallow doublet with different faulting styles
Published: 2020-02-12
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
The increased seismic activity of the last ~10 years in Changning county of Sichuan Province comprised just small (mostly ML < 5.0) injection-induced earthquakes. The MW 5.7 earthquake of June 17, 2019 is the largest event ever reported there. Moment tensor of the mainshock was remarkably dominated by a compensated linear vector dipole. We resolve its fine structure showing it was a doublet, [...]
Impact of topography on earthquake static slip inversions
Published: 2020-02-12
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Our understanding of earthquakes is limited by our knowledge, and our description, of the physics of the Earth. When solving for subsurface fault slip, it is common practice to assume minimum complexity for the Earths characteristics such as topography, fault geometry and elastic properties. These characteristics are difficult to include in simulations and our knowledge of them is incomplete, [...]
Stress Changes on the Garlock fault during and after the 2019 Ridgecrest Earthquake Sequence
Published: 2020-02-09
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
The recent 2019 Ridgecrest earthquake sequence in Southern California jostled the seismological community by revealing a complex and cascading foreshock series that culminated in a M7.1 mainshock. But the central Garlock fault, despite being located immediately south of this sequence, did not coseismically fail. Instead, the Garlock fault underwent post-seismic creep and exhibited a sizeable [...]
Urgent Tsunami Computing
Published: 2020-02-08
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Tsunamis pose a hazard that may strike a coastal population within a short amount of time. To effectively forecast and warn for tsunamis, extremely fast simulations are needed. However, until recently such urgent tsunami simulations have been infeasible in the context of early warning and even for high-resolution rapid post-event assessment. The implementation of efficient tsunami numerical codes [...]
Monitoring seasonal variations in seismic velocity and groundwater levels in Harvey, Western Australia using borehole ambient seismic noise interferometry
Published: 2020-01-30
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
In order to explore the relationships between environmental subsurface changes and seismic velocities, we use nearly four years (2015-2018) of continuous ambient seismic noise data recorded in a multi-level borehole sensor array to measure relative seismic velocity changes at the SW Hub CO2 Geosequestration Site in Harvey, Western Australia using seismic noise interferometry. We find a direct [...]
Post-critical SsPmp and its Applications to Virtual Deep Seismic Sounding (VDSS)–3: Back-projection Imaging of the Crust-Mantle Boundary in a Heterogeneous Lithosphere
Published: 2020-01-25
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Virtual Deep Seismic Sounding (VDSS) uses the arrival time of post-critical SsPmp relative to the direct S wave to infer Moho depth at the Pmp reflection point. Due to the large offset between the virtual source and the receiver, SsPmp is more sensitive to lateral variations of structures than near-vertical phases such as Ps that is used to construct conventional P receiver functions. However, [...]
Seismic source tracking with six degree-of-freedom ground motion observations
Published: 2020-01-18
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Back azimuth (BAz) information can be determined from combined measurements of rotations and translations at a single site. Such six degree-of-freedom (6-DoF) measurements are reasonably stable in delivering similar information compared to a small-scale array of three-component seismometers. Here we investigate whether a 6-DoF approach is applicable to tracking seismic sources. While common [...]
Detection of VLF attenuation in the Earth-ionosphere waveguide caused by X-class solar flares using a global lightning location network
Published: 2020-01-09
Subjects: Astrophysics and Astronomy, Earth Sciences, Geophysics and Seismology, Other Physics, Physical Sciences and Mathematics, Physics, The Sun and the Solar System
Solar flares, energetic particles and Earth-impacting coronal mass ejections enhance ionization in the lower ionosphere, inhibiting radio wave propagation in the Earth-ionosphere waveguide (EIWG). This enhanced ionization is observed locally by ionosondes and GPS/GNSS receivers, but spatial coverage of these observations is limited by receiver location. VLF propagation studies have previously [...]
The mixology of precursory strain partitioning approaching brittle failure in rocks
Published: 2020-01-08
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
We examine the strain accumulation and localization process throughout twelve triaxial compression experiments on six rock types deformed in an X-ray transparent apparatus. In each experiment, we acquire 50-100 tomograms of rock samples at differential stress steps during loading, revealing the evolving 3D distribution of X-ray absorption contrasts, indicative of density. Using digital volume [...]
Back-propagating super-shear rupture in the 2016 Mw7.1 Romanche transform fault earthquake
Published: 2019-12-26
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
How an earthquake rupture propagates strongly influences potentially destructive ground shaking. Complex ruptures often involve slip along multiple faults, masking information on the frictional behaviour of fault zones. Geometrically smooth ocean transform fault plate boundaries offer a favourable environment to study fault dynamics, because strain is accommodated along a single, wide fault zone [...]
Fault-zone damage promotes pulse-like rupture and back-propagating fronts via quasi-static effects
Published: 2019-12-26
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Damage zones are ubiquitous components of faults that may affect earthquake rupture. Simulations show that pulse-like rupture can be induced by the dynamic effect of waves reflected by sharp fault zone boundaries. Here we show that pulses can appear in a highly damaged fault zone even in the absence of reflected waves. We use quasi-static scaling arguments and quasi-dynamic earthquake cycle [...]