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Preprints

Filtering by Subject: Geophysics and Seismology

Mapping surface displacement using a pair of interferograms: comparative study

Stéphanie Dumont, Fernando Lopes, Freysteinn Sigmundsson, et al.

Published: 2020-02-27
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology

Interferometric analysis of Synthetic Aperture Radar satellite images (InSAR) measures only one component of ground deformation, in the satellite line-of-sight direction. In order to fully resolve the three dimensional (3D) ground displacement field, InSAR images acquired with different imaging geometries are required. Despite the increase in the number of SAR missions, an area is most frequently [...]

Geodetic Evidence for a Buoyant Mantle Plume Beneath the Eifel Volcanic Area, NW Europe

Corné Kreemer, Geoffrey Blewitt, Paul M. Davis

Published: 2020-02-25
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology

The volcanism of the Eifel volcanic field (EVF), in west-central Germany, is often considered an example of hotspot volcanism given its geochemical signature and the putative mantle plume imaged underneath. EVF’s setting in a stable continental area provides a rare natural laboratory to image surface deformation and test the hypothesis of there being a thermally buoyant plume. Here we use Global [...]

Subducted oceanic crust as the origin of seismically slow lower-mantle structures

Timothy D. Jones, Ross Maguire, Peter van Keken, et al.

Published: 2020-02-21
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

Mantle tomography reveals the existence of two large low shear velocity provinces (LLSVPs) at the base of the mantle. We examine here the hypothesis that they are piles of oceanic crust that have steadily accumulated and warmed over billions of years. We use existing global geodynamic models in which dense oceanic crust forms at divergent plate boundaries and subducts at convergent ones. The [...]

WORKSHOP REPORT: Securing Legacy Seismic Data to Enable Future Discoveries September 18-19, 2019 Albuquerque, New Mexico

Lorraine J. Hwang, Tim Ahern, Cindy Ebinger, et al.

Published: 2020-02-21
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

On September 18-19, 2019 a workshop on Securing Legacy Data to Enable Future Discoveries was held in Albuquerque, New Mexico engaging 29 researchers representing universities, national laboratories, and governmental agencies that included 4 international and 10 early career participants. The need and funding for this workshop grew out of a June 2018 event focused on legacy seismic data organized [...]

Inchworm-like source evolution through a geometrically complex fault fueled persistent supershear rupture during the 2018 Palu Indonesia earthquake

Ryo Okuwaki, Shiro Hirano, Yuji Yagi, et al.

Published: 2020-02-21
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure

How does fault slip follow an earthquake rupture front propagating faster than the local shear-wave velocity (i.e., at supershear speed)? How does a supershear rupture front pass through a geometrically complex fault system? Resolving the evolution of such complex earthquake ruptures is fundamental to our understanding of earthquake-source physics, but these events have not been well captured by [...]

Processing Seismic Ambient Noise Data with the Continuous Wavelet Transform to Obtain Reliable Empirical Green’s Functions

Yang Yang, Chunyu Liu, Charles A. Langston

Published: 2020-02-21
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

We propose a new data processing flow to compute empirical Green’s functions (EGF) from ambient seismic noise based on a soft thresholding designaling and denoising method using the continuous wavelet transform. The designaling algorithm is carried out during the initial data processing to remove earthquakes and other transient signals in the seismic record. A continuous wavelet transform [...]

Evidence of recurrent mass movement in front of the maximum slip area of the 1960 Chile earthquake: Implications for risk assessment and paleoseismology

Cristian Araya-Cornejo, Matías Carvajal, Jasper Moernaut, et al.

Published: 2020-02-20
Subjects: Earth Sciences, Geology, Geomorphology, Geophysics and Seismology, Physical Sciences and Mathematics

We present evidence that suggests a new risk scenario for the Valdivia basin in south Chile, located in the area of the magnitude 9.5 1960 earthquake. In 1960, three mass movements, triggered by the earthquake shaking, dammed the upper course of the San Pedro River and threatened Valdivia City until it was opened in a controlled manner by its inhabitants. Published historical accounts indicate [...]

Array-based iterative measurements of SmKS travel times and their constraints on outermost core structure

Wenbo Wu, Jessica C. E. Irving

Published: 2020-02-20
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

Vigorous convection in Earths outer core led to the suggestion that it is chemically homogeneous. However, there is increasing seismic evidence for structural complexities close to the outer cores upper and lower boundaries. Both body waves and normal mode data have been used to estimate a P-wave velocity, Vp, at the top of the outer core (the E layer), which is lower than that in the Preliminary [...]

Large-scale crustal structure beneath Singapore using receiver functions from a dense urban nodal array

Karen H Lythgoe, Miranda Ong Su Qing, Shengji Wei

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

Yen Joe Tan, David Marsan

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

Jacqueline Austermann, Christine Y Chen, Harriet Lau, et al.

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

Tadashi Ishikawa, Yusuke Yokota, Shun-ichi Watanabe, et al.

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

Junqing liu, Jiri Zahradnik

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

Leah Langer, Théa Ragon, Anthony Sladen, et al.

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

Marlon Dale Ramos, Jing Ci Neo, Prithvi Thakur, et al.

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 [...]

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