Spring 2023

Fridays at 12:00 PM
E&MS A340

April 7, 2023

Speaker: Felipe Gonzalez, UC Berkeley

Title: A dive into planetary interiors: insights from matter at extreme conditions


April 14, 2023

Speaker: Souvav Kumar, UC Berkeley

Title: Long-term and Continuous Evaluation of the Hydro-geochemical Precursors to Earthquakes in Northeast India


April 21, 2023

Speaker: Mike Wong, UC Berkeley and SETI Institute

Title: Deep Clouds on Jupiter

Abstract: Deep clouds on Jupiter are seen in cyclonic vortices, convective storms, and over a broad high-latitude expanse beyond 45 degrees north. Time-series Hubble imaging, combined with Juno lightning detections, shows that these deep clouds are often associated with convective storms, but they can linger after convection concludes, or appear before it starts. The deep clouds at high latitudes are seen because there is a widespread thinning out of the overlying cloud deck (based on modeling of the HST data combined with simultaneous Gemini infrared imaging). A chemical model of the upper clouds finds that the expected ammonia and ammonium hydrosulfide clouds should form above and below a cloud-free "dead zone" in the 1-2 bar pressure range. The Galileo probe and several remote sensing publications over the years have found cloud opacity within this dead zone, challenging our knowledge of giant planet cloud chemistry. Deep clouds have been used in previous work to estimate the atmospheric water abundance, but because the deep atmospheric temperatures are not precisely known, this method can only be used to show that the water abundance must be at least 0.5 times the solar value.

April 28, 2023

Speaker: Gaspard Farge, UCSC

Title: Sounds of the subduction plumbing system — How transient fluid circulation processes in the subduction shape sources and patterns of seismic tremor


May 5, 2023

Speaker: Yuexin Li, Caltech

Title: lluminating Spatiotemporal Variations of Shallow Fault Creep from Satellite Geodesy: A closer look at the San Francisco Bay Area


May 12, 2023

Speaker: Ettore Biondi, Caltech

Title: Second boiling of the Long Valley Caldera resolved by fiber-seismic tomography

Abstract: Geophysical characterization of calderas is fundamental in assessing their potential for future catastrophic volcanic eruptions. The mechanism behind the unrest of Long Valley Caldera in California remains highly debated, with recent periods of uplift and seismicity driven either by the release of aqueous fluids above the magma chamber or by the intrusion of magma into the upper crust. We employ distributed acoustic sensing data recorded along a 100-km fiber-optic cable traversing the caldera to image its subsurface structure. Our images highlight a definite separation between the shallow hydrothermal system and the large Pleistocene magma chamber intruded at ~12 km depth. The combination of the geological evidence with our results shows how fluids exsolved through second boiling provide the source of the observed uplift and seismicity.


May 19, 2023

Speaker: Tanja Kovacevic, UC Berkeley

Title: Planet Mixology: Stirring the Mantle of Water Worlds

Abstract: Water worlds are exoplanets ranging in size between Earth and Neptune that are predicted to be rich in water. The interior structure of a water world is assumed to have distinct layers: (1) iron core, (2) rocky mantle, and (3) water. This 3-layer model may work in smaller planets where water and rock form differentiated layers with limited incorporation of water into silicates. However, in larger planets water and silicates may interact differently due to greater interior pressures and temperatures found at the rock-ice boundary. Determining the dynamics of these two materials at extreme conditions is necessary for understanding a water world's growth and evolution. In this work, we use density functional molecular dynamics (DFT-MD) simulations to investigate the miscibility and dynamics a major end-member silicate phase bridgmanite (MgSiO3), and water (H2O) at the conditions pertinent to the rock-ice boundary layer within water worlds. We use a heat-until-it-mixes approach to explore pressures ranging from 30–120 GPa and temperatures from 500–8000 K. When temperatures exceed the melting point of bridgmanite, we show that MgSiO3 and H2O mix in all proportions. To provide proof of concept that these conditions are met during the collisional growth of these water-rich bodies, we ran smoothed particle hydrodynamics simulations. We simulated the collisional growth of water worlds via giant impacts between water rich planetesimals of 0.7–4.7 Earth masses. This work provides theoretical evidence that many massive water worlds have mixed mantles.


May 26, 2023

Speaker: Nadine Nettelmann, UCSC

Title: Jupiter interior models and water in the atmosphere

Abstract: The Juno spacecraft measurements of Jupiter's gravity field and equatorial water abundance have expelled conventional models of Jupiter's interior from what has before been hoped to be the ballpark of solutions: The atmospheric water abundance is likely 1-5x solar while most interior models fall way below 1x solar. Before Juno, the conventional view was that of a largely adiabatic interior that is divided into a He-poor outer envelope and a helium- and heavy element-rich metallic deep interior. Meanwhile in the Juno era, models that specifically address the zonal flows, the magnetic field, or the tidal response all arrive at the conclusion of stably stratified layers, although at varying depth. In this IGPP-Seminar I will discuss Jupiter models and propose a new series of interior models. The trail toward super-solar atmospheric water abundance will lead us to the helium reservoir at great depth, the Earth ocean, and the stars. Unavoidably, I will also touch on equations of state.

June 2, 2023

Speaker: Matija Cuk, SETI

Title: A Past Episode of Rapid Tidal Evolution of Enceladus?

Abstract: Saturn possesses a dynamically rich system containing numerous moons and impressive rings. Whether the rings of Saturn are much younger than the planet itself has been a long-open question; more recently a young age has been proposed for some moons. Recent detection of the fast orbital evolution of Rhea and Titan strongly suggest highly frequency-dependent tidal response of Saturn, possibly through excitation of inertial waves within the planet's convective envelope. Taking into account observations and numerical simulations, we argue that nether pure evolution through inertial waves not conventional (equilibrium) tides can explain the Saturnian system. We propose that the system's architecture can best be explain by relatively high "background" tidal response coupled with discrete resonant modes. Assuming that Enceladus went through a temporary period of fast tidal evolution, we can reproduce its present resonance with Dione and satisfy other dynamical constraints.


June 9, 2023

Speaker: Guo Cheng, UCSC

Title: Geodetic Investigations of Inelastic Earthquake Cycle Deformation at the Makran Subduction Zone

Intro: In many numerical modeling studies of the Earth system. Crustal deformation in response to earthquake rupture is assumed to be an elastic process, where earthquake-induced strain is recoverable after several earthquake cycles. Inelastic deformation, or permanent damages caused by the earthquake are ignored in under the elastic assumption, leading to inaccurate estimation of earthquake hazard potential, earthquake mechanisms, or fault zone properties. This presentation focuses on revealing the inelastic behaviors of the Earth during or after large earthquakes, through the application of satellite-based geodetic observations and numerical modeling techniques.