Filtering by Subject: Geophysics and Seismology

Bridging spatiotemporal scales of fault growth during continental extension

Sophie Pan, John Naliboff, Rebecca E. Bell, et al.

Published: 2021-04-21
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Other Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure

Continental extension is accommodated by the development of kilometre-scale normal faults, which grow by accumulating metre-scale earthquake slip over millions of years. Reconstructing the entire lifespan of a fault remains challenging due to a lack of observational data with spatiotemporal scales that span the relatively short-term earthquake cycle, and the longer-term paleoseismic record. Using [...]

The 2019-2020 Southwest Puerto Rico earthquake sequence: seismicity and faulting

Blaž Vičič, Seyyedmaalek Momeni, Alessandra Borghi, et al.

Published: 2021-04-20
Subjects: Geophysics and Seismology, Tectonics and Structure

The 2019-2020 Southwest Puerto Rico earthquake sequence ruptured multiple faults with several moderate magnitude earthquakes. Here we investigate the seismotectonics of this fault system using high precision hypocenter relocation and inversion of the near-field strong motions of five largest events in the sequence (5.6≤Mw≤6.4) for kinematic rupture models. The Mw6.4 mainshock occurred on an NE [...]

The Mid-Lithospheric Discontinuity caused by channel flow in the cratonic lithosphere

Haibin Yang, Irina Artemieva, Hans Thybo

Published: 2021-04-20
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure

Stable cratons with a thick (> 200 km) and cold lithosphere form rheologically strong plates that move atop a ductile asthenospheric mantle. Various types of seismic observations show the presence of a potentially rheologically weak zone at depths of ca. 80 – 150 km termed the Mid-Lithosphere Discontinuity (MLD). While various mechanisms may explain the MLD, the dynamic processes leading to the [...]

Structure and Stress Field of the Lithosphere between Pamir and Tarim

Wasja Bloch, Bernd Schurr, Xiaohui Yuan, et al.

Published: 2021-04-14
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure

The Pamir plateau protrudes ~300 km between the Tajik- and Tarim-basin lithosphere of Central Asia. Whether its salient location and shape are caused by forceful indentation of a promontory of Indian mantle lithosphere is debated. We present a new local-seismicity and focal-mechanism catalog, and a P-wave velocity model of the eastern part of the collision system. The data suggest a [...]

Microstructural differences between naturally-deposited and laboratory beach sands

Amy Ferrick, Vashan Wright, Michael Manga, et al.

Published: 2021-04-14
Subjects: Civil and Environmental Engineering, Civil Engineering, Earth Sciences, Engineering, Geophysics and Seismology, Geotechnical Engineering, Physical Sciences and Mathematics, Sedimentology

The orientation of and contacts between grains of sand reflect the processes that deposit the sands. Grain orientation and contact geometry also influence mechanical properties. Quantifying and understanding sand microstructure thus provide an opportunity to understand depositional processes better and connect microstructure and macroscopic properties. We compare naturally-deposited beach sands [...]

The morphology, evolution and seismic visibility of partial melt at the core-mantle boundary: Implications for ULVZs

Juliane Dannberg, Robert Myhill, Rene Gassmoeller, et al.

Published: 2021-04-14
Subjects: Geophysics and Seismology

Seismic observations indicate that the lowermost mantle above the core-mantle boundary is strongly heterogeneous. Body waves reveal a variety of ultra-low velocity zones (ULVZs), which extend not more than 100 km above the core-mantle boundary and have shear velocity reductions of up to 30%. While the nature and origin of these ULVZs remain uncertain, some have suggested they are evidence of [...]

Probing the DPRK nuclear test-site down to low seismic magnitude

Steven John Gibbons, Tormod Kværna, Sven Peter Näsholm, et al.

Published: 2021-04-14
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

On 3 September 2017, the Democratic People’s Republic of Korea (DPRK) carried out its sixth declared underground nuclear test (NK6) at the Punggye‐ri test site. With body‐wave magnitude 6.1, this explosion was significantly larger than any of the previous five explosions, and it has been followed by numerous smaller seismic events. The explosion generated seismic waves dominated by significantly [...]

Imaging the seismic velocity structure of the crust and upper mantle in the northern East African Rift using Rayleigh wave tomography

Emma Louise Chambers, Nicholas Harmon, Catherine Rychert, et al.

Published: 2021-04-13
Subjects: Geophysics and Seismology

Within the northern East African Rift, multiple seismic models have been produced to understand the evolution of magmatism, however variations in method, resolution, and scale make direct comparisons challenging. The lack of instrumentation off rift further limits our understanding of the spatial extent of tectonic and magmatic processes, which is crucial to understanding magmatic continental [...]

Orbital, the Box - An interactive educational tool for in-depth understanding of astronomical climate forcing.

Bryan C. Lougheed

Published: 2021-04-07
Subjects: Adult and Continuing Education, Astrophysics and Astronomy, Climate, Earth Sciences, Education, Educational Methods, Geology, Geophysics and Seismology, Higher Education, Instructional Media Design, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics, The Sun and the Solar System

“Orbital, the Box” provides an interactive tool with graphical user interface (GUI) for stimulating active, visual learning for understanding of astronomical climate forcing. This cross-platform tool can be run locally on a personal computer using a standard web browser environment with no need for plugins, thus maximising accessibility for students and teachers alike. The tool facilitates in the [...]

Coulomb Threshold Rate-and-State Model for Fault Reactivation: Application to induced seismicity at Groningen

Elias Rafn Heimisson, Jonathan D Smith, Jean-Philippe Avouac, et al.

Published: 2021-04-06
Subjects: Environmental Monitoring, Geophysics and Seismology, Tectonics and Structure

A number of recent modeling studies of induced seismicity have used the rate-and-state friction model of Dieterich (1994) to account for the fact that earthquake nucleation is not instantaneous. Notably, the model assumes a population of seismic sources accelerating towards instability with a distribution of intial slip speeds such that they would produce earthquakes steadily in absence of any [...]

Dilatancy and compaction of a rate-and-state fault in a poroelastic medium: Linearized stability analysis

Elias Rafn Heimisson, John Rudnicki, Nadia Lapusta

Published: 2021-04-06
Subjects: Applied Mathematics, Geophysics and Seismology, Tectonics and Structure

Faults in the crust at seismogenic depths are embedded in a fluid-saturated, elastic, porous material. Slip on such faults may induce transient pore pressure changes through dilatancy or compaction of the gouge or host rock. However, the poroelastic nature of the crust and the full coupling of inelastic gouge processes and the host rock have been largely neglected in previous analyses. Here, we [...]

Crustal-scale listric geometry of the San Andreas Fault driven by lower crustal flow

Haibin Yang, Louis N. Moresi, Mark Quigley

Published: 2021-03-31
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Physical Sciences and Mathematics

The San Andreas Fault (SAF) is one of the dominant components of the transform boundary between the Pacific and the North American Plate. Although the fault is verti-cal-to sub-vertical at shallow (<10 km) depth, it variably dips at angles of ca. 40-70º to the southwest near the western Transverse Range and to the northeast in its southern seg-ment at depths of ca. 10-20 km, and thus can be [...]

Resolving Northern Alaska Earthquake Sequences Using the Transportable Array and Probabilistic Location Methods

Steven John Gibbons, Natalia Ruppert, Ezgi Karasözen, et al.

Published: 2021-03-25
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure

Between 2014 and 2017, almost 200 new seismic stations were installed in Alaska and northwestern Canada as part of the EarthScope USArray Transportable Array. These stations currently provide an unprecedented capability for the detection and location of seismic events in regions with otherwise relatively sparse station coverage. Two interesting earthquake sequences in 2018 and 2019 in the [...]

Slab temperature evolution over the lifetime of a subduction zone

Adam F Holt, Cailey Brown Condit

Published: 2021-03-25
Subjects: Earth Sciences, Geophysics and Seismology

The thermal evolution of subducting slabs controls a range of subduction processes, yet we lack a robust understanding of how thermal structure develops over a subduction zone’s lifetime. We investigate the time-dependence of slab thermal structure using dynamically consistent, time evolving models. Pressure-temperature (P-T) conditions along the slab Moho and slab top exhibit substantial [...]

Recrystallization of ice enhances the creep and vulnerability to fracture of ice shelves

Meghana Ranganathan, Brent Minchew, Colin R. Meyer, et al.

Published: 2021-03-08
Subjects: Earth Sciences, Geophysics and Seismology, Glaciology, Physical Sciences and Mathematics

The initiation of fractures and fast flow in floating regions of Antarctica have the potential to destabilize large regions of the grounded ice sheet, leading to significant sea-level rise. While observations have shown rapid, localized deformation and damage in the margins of fast-flowing glaciers, there remain gaps in our understanding of how rapid deformation affects the viscosity and [...]


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