Preprints
Filtering by Subject: Geophysics and Seismology
Real-Time High-Rate GNSS Displacements: Performance Demonstration During the 2019 Ridgecrest, CA Earthquakes
Published: 2019-08-17
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Traditional real-time seismology has relied on inertial sensors to characterize ground motions and earthquake sources, particularly for hazards applications such as warning systems. In the past decade, a revolution in high-rate, real-time Global Navigation Satellite System (GNSS) displacement have provided a new source of data to augment traditional measurement devices. The Ridgecrest, California [...]
Empirical Green’s Function Retrieval using Cross-correlation of Ambient Noise Correlations (C2)
Published: 2019-08-12
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Empirical Greens function (EGF) retrieval commonly relies on cross-correlating the long-term ambient seismic wavefield that is simultaneously recorded at multiple stations. Recent studies have demonstrated observationally that cross-correlating the coda of ambient noise cross-correlation functions (C3) enables reconstruction of the EGFs, regardless of the operating time of the stations. In this [...]
Small baseline InSAR time series analysis: Unwrapping error correction and noise reduction
Published: 2019-08-07
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We present a review of small baseline interferometric synthetic aperture radar (InSAR) time series analysis with a new processing workflow and software implemented in Python, named MintPy (https://github.com/insarlab/MintPy). The time series analysis is formulated as a weighted least squares inversion. The inversion is unbiased for a fully connected network of interferograms without multiple [...]
Introduction of covariance components in slip inversion of geodetic data following a non-uniform spatial distribution and application to slip deficit rate estimation in the Nankai Trough subduction zone
Published: 2019-08-02
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
When spatial distribution of observation stations has bias in geodetic slip inversion, modeling errors in the inversion scheme may result in significant unnatural short-wave components in estimated slip distribution, which overfit to data. Combined use of both land and seafloor geodetic data in slip inversion often leads to such situations. To avoid overfitting, I proposed a method to [...]
Fracture and Weakening of Jammed Subduction Shear Zones, Leading to the Generation of Slow Slip Events
Published: 2019-07-31
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Geodetic data have revealed that parts of subduction interfaces creep steadily or transiently. Transient slow slip events (SSEs) are typically interpreted as aseismic frictional sliding. However, SSEs may also occur via mixed visco‐brittle deformation, as observed in shear zones containing mixtures (mélange) of strong fractured clasts embedded in a weak visco‐brittle matrix. We test the [...]
Basal melting over Subglacial Lake Ellsworth and it catchment: insights from englacial layering
Published: 2019-07-25
Subjects: Earth Sciences, Geophysics and Seismology, Glaciology, Hydrology, Physical Sciences and Mathematics
Deep-water ‘stable’ subglacial lakes likely contain microbial life adapted in isolation to extreme environmental conditions. How water is supplied into a subglacial lake, and how water outflows, is important for understanding these conditions. Isochronal radio-echo layers have been used to infer where melting occurs above Lake Vostok and Lake Concordia in East Antarctica but have not been used [...]
Geostatistical characterisation of internal structure of mass-transport deposits from seismic reflection images and borehole logs
Published: 2019-07-24
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Seismic reflection images of mass-transport deposits often show apparently chaotic, disorded or low-reflectivity internal seismic facies. The lack of laterally coherent reflections can prevent horizon-based interpretation of internal structure. This study instead inverts for geostatistical parameters which characterise the internal heterogeneity of mass-transport deposits from depth-domain [...]
Investigating the role of faults in fluid migration and gas hydrate formation along the southern Hikurangi Margin, New Zealand
Published: 2019-07-22
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
The Hikurangi Margin off the east coast of the North Island (Te Ika-a-Māui) is a tectonically active subduction zone and the location of New Zealand’s largest gas hydrate province. Faults are internally complex volumetric zones that may play a significant role in the migration of fluids beneath the seafloor. The combined processes of deformation and fluid migration result in the formation of [...]
Are we in the right path in using early warning systems?
Published: 2019-07-22
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
This article focusses on the recent tsunami in Indonesia, and the factors led to a large number of fatalities. We also discussed the failure of early warning systems, steps, methods and technologies, in general, to improve the early warning systems in the future to mitigate the loss of lives and property during these impending disasters. This article is timely as Indonesia has seen one of the [...]
Urban Seismic Site Characterization by Fiber-Optic Seismology
Published: 2019-07-16
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Accurate ground-motion prediction requires detailed site effect assessment, but in urban areas where such assessments are most important, geotechnical surveys are difficult to perform, limiting their availability. Distributed acoustic sensing (DAS) offers an appealing alternative by repurposing existing fiber-optic cables, normally employed for telecommunication, as an array of seismic sensors. [...]
The moment duration scaling relation for slow rupture arises from transient rupture speeds
Published: 2019-07-16
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
The relation between seismic moment and earthquake duration for slow rupture follows a different power law exponent than sub-shear rupture. The origin of this difference in exponents remains unclear. Here, we introduce a minimal one-dimensional Burridge-Knopoff model which contains slow, sub-shear and super-shear rupture, and demonstrate that different power law exponents occur because the [...]
Influence of fault roughness on surface displacement: from numerical simulations to coseismic slip distributions
Published: 2019-07-10
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Field studies characterized early on natural faults as rough, i.e. non-planar at all scales. Fault roughness induces local stress perturbations, which dramatically affect rupture behavior, resulting in slip heterogeneity. The relation between fault roughness and produced slip remains, however, a key knowledge gap in current numerical and field studies. In this study, we analyze numerical [...]
Seismological evidence for subcrustal magmatic injection beneath Fogo volcano, Cape Verde hotspot
Published: 2019-07-09
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Volcanology
Fogo volcano belongs to the Cape Verde hotspot and its most recent eruption occurred from November 2014 to February 2015. From January to December 2016 we operated a temporary seismic network on Fogo and were able to locate 289 earthquakes in total. While most of the events occur at distances > 25 km near the neighboring island of Brava. However, on 15th August 2016 we recorded an isolated [...]
Photonic seismology in Monterey Bay: Dark fiber DAS illuminates offshore faults and coastal ocean dynamics
Published: 2019-07-09
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Emerging fiber-optic sensing technology coupled to existing subsea telecommunications cables can provide access to unprecedented seafloor observations of both ocean and solid earth phenomena. During March 2018, we conducted a Distributed Acoustic Sensing (DAS) measurement campaign along a buried fiber-optic cable typically used for data transfer to and from a scientific cabled observatory [...]
Denoising ambient seismic field correlation functions with convolutional autoencoders
Published: 2019-07-04
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Seismic interferomestry is an established method for monitoring the temporal evolution of the Earths physical properties. We introduce a new technique to improve the precision and temporal resolution of seismic monitoring studies based on deep learning. Our method uses a convolutional denoising autoencoder, called ConvDeNoise, to denoise ambient seismic field correlation functions. The technique [...]