Preprints
Filtering by Subject: Geophysics and Seismology
The 2019-2020 Southwest Puerto Rico earthquake sequence: seismicity and faulting
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
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
Published: 2021-04-15
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
Published: 2021-04-15
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
Published: 2021-04-15
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
Published: 2021-04-15
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
Published: 2021-04-14
Subjects: Geophysics and Seismology
Understanding the dynamics and evolution of continental rifting is broadly important for our understanding of plate tectonics. The northern East African Rift offers an excellent opportunity to study these processes at an active rift that was initiated by a large magmatic event. Multiple seismic models have been produced to understand the evolution of magmatism which image punctuated slow velocity [...]
Orbital, the Box - An interactive educational tool for in-depth understanding of astronomical climate forcing.
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
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 the absence of [...]
Dilatancy and compaction of a rate-and-state fault in a poroelastic medium: Linearized stability analysis
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
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
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
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
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 [...]
New insight into post-seismic landslide evolution processes in the tropics
Published: 2021-03-05
Subjects: Earth Sciences, Geomorphology, Geophysics and Seismology, Hydrology
Earthquakes do not only trigger landslides in co-seismic phases but also elevate post-seismic landslide susceptibility either by causing a strength reduction in hillslope materials or by producing co-seismic landslide deposits, which are prone to further remobilization under the external forces generated by subsequent rainfall events. However, we still have limited observations regarding the [...]