Geology topics

Charles Williams

Publications and source records attributed to Charles Williams.

3 recordsLinked to original sources

USGS2024

2024 Crustal Deformation Modeling Workshop report

The 2024 Crustal Deformation Modeling Workshop was held June 10–14 at the Colorado School of Mines. The workshop included two days of tutorials on using PyLith for crustal deformation modeling, followed by three days of science talks and discussions. The workshop focused on four primary themes: ● Constraining long-term fault slip rates and their uncertainties using geodetic and geologic data; ● Earthquake cycle modeling with a focus on constraining models using seismic and geodetic data; ● Interaction of fluids and faulting; and ● Separating contributions of surface loading and tectonic loading in crustal deformation. The complete agenda is available on the CIG website.

Conference Paper↗

USGS2023

2022 Crustal Deformation Modeling Workshop Report

The 2022 Crustal Deformation Modeling Workshop was held June 20–24 at the Colorado School of Mines in Golden, Colorado. The workshop included two days of tutorials on the use of the open-source software PyLith for crustal deformation modeling followed by three days of science talks and discussions. The workshop focused on three primary themes: (1) Earthquake cycle modeling; (2) Inversions for fault slip; and (3) Faulting, fluids, and surface loading. The talks highlighted how computational models provide insight into intriguing observations of Earth and planetary behavior. These included (1) earthquake synchronization of rupture patches due to their close proximity to each other, (2) the influence of fault geometry and damage zones on hypocenter depth and rupture propagation, (3) a lack of steady-state faulting behavior due to long time scales for grain size evolution in the mid-crust, (4) crustal deformation due to tidal, hydrological, and atmospheric loads, and (5) plumes of gas and icy particles due to tidal driven faulting on Enceladus (one of Saturn’s moons). The talks also described new computational modeling capabilities for incorporating complex geologic structure into Bayesian inversions for fault slip and efficient implementation of earthquake cycle models using a symmetric interior discontinuous Galerkin method. The complete agenda is available on the Computational Infrastructure for Geodynamic (CIG) website.

Report↗

USGS2019

Dynamically triggered changes of plate interface coupling in Southern Cascadia

In Southern Cascadia, precise Global Navigation Satellite System (GNSS) measurements spanning about 15 years reveal steady deformation due to locking on the Cascadia megathrust punctuated by transient deformation from large earthquakes and episodic tremor and slip events. Near the Mendocino Triple Junction, however, we recognize several abrupt GNSS velocity changes that reflect a different process. After correcting for earthquakes and seasonal loading, we find that several dozen GNSS time series show spatially coherent east‐west velocity changes of ~2 mm/yr and that these changes coincide in time with regional M > 6.5 earthquakes. We consider several hypotheses and propose that dynamically triggered changes in megathrust coupling best explain the data. Our inversions locate the coupling changes slightly updip of the tremor‐producing zone. We speculate that fluid exchange surrounding the tremor region may be important. Such observations of transient coupling changes are rare and challenging to explain mechanistically but have important implications for earthquake processes on faults.

California↗