Preprints
Filtering by Subject: Geophysics and Seismology
Vibrational modes of hydraulic fractures: Inference of fracture geometry from resonant frequencies and attenuation
Published: 2018-05-27
Subjects: Earth Sciences, Environmental Sciences, Geophysics and Seismology, Glaciology, Physical Sciences and Mathematics, Volcanology
Oscillatory seismic signals arising from resonant vibrations of hydraulic fractures are observed in many geologic systems, including volcanoes, glaciers and ice sheets, and hydrocarbon and geothermal reservoirs. To better quantify the physical dimensions of fluid‐filled cracks and properties of the fluids within them, we study wave motion along a thin hydraulic fracture waveguide. We present a [...]
Crack models of repeating earthquakes predict observed moment-recurrence scaling
Published: 2018-05-24
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Small repeating earthquakes are thought to represent rupture of isolated asperities loaded by surrounding creep. The observed scaling between recurrence interval and seismic moment, Tr ~ M^(1/6), contrasts with expectation assuming constant stress drop and no aseismic slip (Tr ~ M^(1/3)). Here we demonstrate that simple crack models of velocity-weakening asperities embedded in a [...]
Time scales of shallow magma chamber replenishment at Campi Flegrei caldera.
Published: 2018-05-23
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Volcanology
Ascent of primitive magmas from depth into shallow, partially degassed reservoirs is commonly assumed to be a viable eruption trigger. The resulting processes of convection and mixing have played an important role both in pre- and syn-eruptive stages in many eruptions of different sizes at the unrest Campi Flegrei caldera in Southern Italy. We performed numerical simulations of magma chamber [...]
Measuring Higher-Mode SurfaceWave Dispersion Using a Transdismensional Bayesian Approach
Published: 2018-05-21
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We present a method for measuring the dispersion of higher mode surface wave phase velocities from a single seismogram using a hierarchical transdimensional Bayesian approach. The 1-D shear velocity profiles down to 800km depth between sources and seismic stations are regarded as the controlling parameters to tune the phase velocities of fundamental and higher modes. The misfits between [...]
Determination of the Lithosphere-Asthenosphere Boundary using program LABWA2015
Published: 2018-05-09
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Lithosphere-Asthenosphere Boundary (LAB) is a lower boundary of the lithospheric plate, so, it is an important tectonic boundary. We present the package of numerical program LABWA2015 developed for simple calculations of position of LAB. It assumes isostatic state and uses gravity as well as topographic data. However, program provides better results if additional geophysical data are used, e.g. [...]
Combined geophysical measurements provide evidence for unfrozen water in permafrost in the Adventdalen valley in Svalbard
Published: 2018-05-07
Subjects: Earth Sciences, Geophysics and Seismology, Hydrology, Other Earth Sciences, Physical Sciences and Mathematics
Quantifying the unfrozen water content of permafrost is critical for assessing impacts of surface warming on the reactivation of groundwater flow and release of greenhouse gasses from degrading permafrost. Unfrozen water content was determined along a ~12 km transect in the Adventdalen valley in Svalbard, an area with continuous permafrost, using surface nuclear magnetic resonance and controlled [...]
Identifying causes of ground-penetrating radar reflections using time-domain reflectometry and sedimentological analyses
Published: 2018-05-07
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Sedimentology
Ground-penetrating radar (GPR) is a geophysical technique widely used to study the shallow subsurface and identify various sediment features that reflect electromagnetic waves. However, little is known about the exact cause of GPR reflections because few studies have coupled wave theory to petrophysical data. In this study, a 100- and 200-MHz GPR survey was conducted on aeolian deposits in a [...]
Tracking CO2 plumes in clay-rich rock by distributed fiber optic strain sensing (DFOSS): a laboratory demonstration
Published: 2018-04-25
Subjects: Earth Sciences, Environmental Monitoring, Environmental Sciences, Fluid Dynamics, Geology, Geophysics and Seismology, Hydrology, Mineral Physics, Oil, Gas, and Energy, Optics, Physical Sciences and Mathematics, Physics
Monitoring the migration of pore pressure, deformation, and saturation plumes with effective tools is important for the storage and utilization of fluids in underground reservoirs, such as geological stores of carbon dioxide (CO2) and natural gas. Such tools would also verify the security of the fluid contained reservoir–caprock system. Utilizing the swelling strain attributed to pressure [...]
Strain budget of the Ecuador-Colombia subduction zone: a stochastic view
Published: 2018-04-24
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
The 2016 Pedernales earthquake (Mw=7.8) ruptured a portion of the Colombia-Ecuador subduction interface where several large historical earthquakes have been documented since the great 1906 earthquake (M=8.6). Considering all significant ruptures that occurred in the region, it has been suggested that the cumulative moment generated co-seismically along this part of the subduction over the last [...]
Detecting lightning infrasound using a high-altitude balloon
Published: 2018-04-17
Subjects: Atmospheric Sciences, Earth Sciences, Geophysics and Seismology, Meteorology, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics
Acoustic waves with a wide range of frequencies are generated by lightning strokes during thunderstorms, including infrasonic waves (0.1 to 20 Hz). The source mechanism for these low frequency acoustic waves is still debated and studies have so far been limited to ground-based instruments. Here we report the first confirmed detection of lightning generated infrasound with acoustic instruments [...]
Topography and the shallow slip deficit inference
Published: 2018-04-13
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Images of earthquake slip serve as the foundation for understanding the distribution of coseismic energy release, theories about rupture propagation, and fault mechanics. Geodetic slip images are inferred using elastic models that link surface observations to fault activity at depth. To date, almost all elastic models used for these common calculations [10, 14, 19, 23] include the assumption that [...]
Rapid mantle flow with power-law creep explains deformation after the 2011 Tohoku mega-quake
Published: 2018-04-11
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
The deformation transient that follows large subduction zone earthquakes is thought to originate from the interaction of viscoelastic flow in the asthenospheric mantle and slip on the megathrust that are both accelerated by the sudden coseismic stress change. The surface deformation following the 2011 Mw 9.0 Tohoku earthquake provides some of the most comprehensive constraints on surface [...]
Constraints on North Anatolian Fault zone width in the crust and upper mantle from S-wave teleseismic tomography
Published: 2018-04-09
Subjects: Earth Sciences, Geophysics and Seismology, Life Sciences, Physical Sciences and Mathematics
We present high resolution S‐wave teleseismic tomography images of the western segment of the North Anatolian Fault (NAFZ) in Turkey using teleseismic data recorded during the deployment period of the DANA array. The array comprised 66 stations with a nominal station spacing of 7 km, thus permitting a horizontal and vertical resolution of approximately 15 km. We use the current S‐wave results [...]
Asthenosphere flow modulated by megathrust earthquake cycles
Published: 2018-04-03
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Subduction megathrusts develop the largest earthquakes, often close to large population centers. Understanding the dynamics of deformation at subduction zones is therefore important to better assess seismic hazards. Here, I develop consistent earthquake cycle simulations that incorporate localized and distributed deformation based on laboratory-derived constitutive laws by combining boundary and [...]
Time-dependent compaction as a mechanism for regular stick-slips
Published: 2018-03-27
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Owing to their destructive potential, earthquakes receive considerable attention from laboratory studies. In friction experiments, stick-slips are studied as the laboratory equivalent of natural earthquakes, and numerous attempts have been made to simulate stick-slips numerically using the Discrete Element Method (DEM). However, while laboratory stick-slips commonly exhibit regular stress drops [...]