Preprints
Filtering by Subject: Geophysics and Seismology
Space-time stress variations on the Palu-Koro fault impacting the 2018 Mw 7.5 Palu earthquake and its seismic hazards
Published: 2020-03-09
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
In this study we calculated the Coulomb stress change before and after the 2018 Palu earthquake (Mw7.5) induced by historical large earthquakes on and around the Palu‐Koro fault (PKF) within Sulawesi Island, Indonesia. We found that the 1996 earthquake (Mw7.9) on the Minahassa thrust likely promoted the 2018 Palu earthquake by stress loading on its hypocenter. Stress shadows in the PKF impacted [...]
Improving the retrieval of offshore-onshore correlation functions with machine learning
Published: 2020-03-07
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
The retrieval of reliable offshore-onshore correlation functions is critical to improve our ability to predict long-period ground motions from megathrust earthquakes. However, localized ambient seismic field sources between offshore and onshore stations can bias correlation functions and generate non-physical arrivals. We present a two-step method based on unsupervised learning to improve the [...]
Stress drop variation of deep-focus earthquakes based on empirical Greens function
Published: 2020-03-04
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We analyze source characteristics of global, deep-focus (> 350 km) earthquakes with moment magnitudes (Mw) larger than 6.0-8.2 using teleseismic P-wave and S-wave spectra and an empirical Greens functions approach. We estimate the corner frequency assuming Brunes source model and calculate stress drops assuming a circular crack model. Based on P-wave and S-wave spectra, the one-standard [...]
Dynamic fault interaction during a fluid-injection induced earthquake: The 2017 Mw 5.5 Pohang event
Published: 2020-03-03
Subjects: Earth Sciences, Geophysics and Seismology, Life Sciences, Physical Sciences and Mathematics
The November 15th, 2017 Mw 5.5 Pohang earthquake (South Korea) has been linked to hydraulic stimulation and fluid injections, making this the largest induced seismic event associated with an Enhanced Geothermal System (EGS). To understand its source dynamics and fault interactions, we conduct the first 3D high-resolution spontaneous dynamic rupture simulations of an induced earthquake. We account [...]
Effect of fault damage zones on long-term earthquake behavior on mature strike-slip faults
Published: 2020-03-03
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Mature strike-slip faults are usually surrounded by a narrow zone of damaged rocks characterized by low seismic wave velocities. Observations of earthquakes along such faults indicate that seismicity is highly concentrated within this fault damage zone. However, the long-term influence of the fault damage zone on complete earthquake cycles, i.e., years to centuries, is not well understood. We [...]
Analytical prediction of seismicity rate due to tides and other oscillating stresses
Published: 2020-03-03
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Planetary Geophysics and Seismology, Planetary Sciences, Tectonics and Structure
Oscillatory stresses are ubiquitous on earth and other solid-surface bodies. Tides and seasonal signals perpetually stress faults in the crust. Relating seismicity to these stresses offers fundamental insight into earthquake triggering. We present a simple model that describes seismicity rate due to perpetual oscillatory stresses. The model applies to large amplitude, non-harmonic, and [...]
Critical fluid injection volumes for uncontrolled fracture ascent
Published: 2020-03-03
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Hydro-fracturing is a routine industrial technique whose safety depends on fractures remaining confined within the target rock volume. Both observations and theoretical models show that, if the fluid volume is larger than a critical value, pockets of fluid can propagate large distances in the Earths crust in a self-sustained, uncontrolled manner. Existing models for such critical volumes are [...]
Mapping surface displacement using a pair of interferograms: comparative study
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
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
Published: 2020-02-22
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
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
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
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
Published: 2020-02-21
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
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 [...]