BENJAMIN IDINI

Welcome to my website

I am a Planetary Scientist currently appointed as a Vera Rubin Postdoctoral Fellow in the Astronomy and Astrophysics Department at UC Santa Cruz. My research interests spand the multi-scale physics of planetary processes in various bodies across the Solar System and beyond, most recently earthquakes on Earth, the ocean dynamics of icy satellites, and the dynamic interiors and formation of giant planets. Most of my work involves building models to translate spacecraft measurements into scientific stories. I also work at constructing physics-based scenarios of how exotic environments in other worlds are maintained, generating predictions that future NASA/ESA interplanetary missions can test and evaluate. I dream with a future where we understand how planets initially form and later evolve and how those processes relate to the origin and survival of life.

I developed my first connection to space as a kid by looking at the clear nightskies of Chiloe Island and the Chilean Patagonia. I initiated my academic path in engineering at the University of Chile, and turned into science trying to understand the large M8.8 Chile earthquake that struck my country of origin in 2010. I received my doctorate degree in Planetary Science from Caltech in 2022, the institution that opened my path into space exploration. I am currently a member of the science teams of NASA missions Juno and Europa Clipper. I am also a science communicator in both English and my native Spanish.

research

Tidal theory of the gas giant planets

Since 2016, the Juno spacecraft has been orbiting Jupiter and collecting a unique data set of Jupiter's tidal Love numbers, namely the tidal response of Jupiter to the masses of the Galilean satellites in orbit around Jupiter. In a pioneering work, I further developed the theory of dynamical tides applied to gas giant planets (Idini and Stevenson, 2021), a body of knowledge that had not been touched since 1984 (Vorontsov+, 1984). In this theoretical rebirth of Jovian dynamical tides, I showed that the tidal Love number k2 measured by Juno was compatible with a modification on the tidal flow produced by the Coriolis force in a rapidly rotating gas giant planet (Idini and Stevenson, 2021). Paired with the Juno observation, these theoretical results constitute the first detection of dynamical tides in a gas giant planet.

Additional Love numbers were reported by Juno after the arrival of the k2 retrievals. The high-degree tides represented in k42 are not only harder to observe, but are also harder to interpret. I applied first-order perturbation theory to develop a fully analytical theory to illuminate the interpretation of k42 (Idini and Stevenson, 2022a). This theory shows how the oblate figure of Jupiter resulting from rapid rotation couples the tides to the rotational response, resulting in an order of magnitude enhancement in k42 (Wahl+, 2020, Idini and Stevenson, 2022a). The resulting k42 enhancement gives rise to an anomaly after comparing models with the Juno k42 observation.

The tidal imprint of a dilute core hosted in Jupiter

In the traditional view of gas giant planet interiors, an envelope of H-He fluid covers a compact core of rocky and icy material. This traditional view nicely emerges from the standard model of planet formation via core accretion. However, even to this day, no geophysical evidence exists to validate the traditional view.

The zonal gravitational field (i.e., non tidal) observed by Juno suggests that Jupiter hosts a dilute core that may extend as far as ~0.6R (Militzer+, 2022). A less extended dilute core could also explain the data when using a different equation of state for the H-He fluid (Miguel+, 2022). Avoiding the uncertainties related to the equation of state, I used Jovian dynamical tides and normal modes to show that internal gravity waves trapped in an extended dilute core (~0.7R) reconcile the anomaly in Juno's k42 observation (Idini and Stevenson, 2022b). This proposed scenario invokes a resonance between Jupiter's internal gravity waves and the orbital motion of the satellite Io.

Theoretical and computational earthquake mechanics

The nucleation, propagation, and arrest of earthquakes remains a fundamental but still unsolved problem in geophysics. Motivated by seismological and geodetic observations of rock damage near fault zones, I expanded a spectral boundary integral method (Luo+, 2017) to numerically model earthquake cycles and rupture propagation in an elastic medium that accounts for the damaged rock that surrounds fault zones. My work has identified a new mechanism to earthquake pulses, a common rupture propagation mode observed during large destructive earthquakes (Idini and Ampuero, 2020).

Earthquake ground-motion characterization

Active seismic regions require accurate characterizations of earthquake ground motion to minimize human and material losses during potentially destructive events. I built a statistical model to forecast the ground motion produced during destructive earthquakes in Chile that is routinely used in seismic hazard studies (Idini+, 2017).

Spaceborne reconstruction of earthquake sources

After the 2019 Ridgecrest earthquake that ended ~20 yr of seismic quiescence in California, I produced a reconstruction of coseismic fault slip using Bayesian methods, satellite radar maps of surface deformation, and GPS displacements (Ross+, 2019). This model has become a prime reference to the characterization of this large and complicated earthquake.

Publications

(12) Idini, B. & Nimmo F. (2024). Resonant stratification in Titan's global ocean. The Planetary Science Journal. [PDF]

(11) Idini, B., Ruiz, S., Ampuero., J-P., Rivera, E, & Leyton, F. (2024). Double distance dependence in high--frequency ground motion along the plate boundary in Northern Chile. Journal of South American Earth Sciences, 133. [PDF]

(10) Idini, B. & Stevenson D.J. (2022). The gravitational imprint of an interior-orbital resonance in Jupiter-Io, The Planetary Science Journal.
[PDF]

(9) Idini, B. & Stevenson D.J. (2022). The lost meaning of Jupiter's high-degree Love numbers, The Planetary Science Journal.
[PDF] [Notebook]

(8) Idini, B. & Stevenson D.J. (2021). Dynamical tides in Jupiter as revealed by Juno, The Planetary Science Journal.
[PDF] [Press1] [Press2]

(7) Erickson, B., Jiang, J., et al., including Idini, B. (2020). The community code verification exercise for simulating sequences of earthquakes and aseismic slip (SEAS), Seismological Research Letters.

(6) Idini, B. & Ampuero J.-P. (2020). Fault-zone damage promotes pulse-like rupture and back-propagating fronts via quasi-static effects, Geophysical Research Letters.
[PDF] [Supporting Information] [Software] [Press]

(5) Ross, Z., Idini, B., Jia, Z., et al. (2019). Hierarchical interlocked orthogonal faulting in the 2019 Ridgecrest earthquake sequence, Science.
[Supplementary Material] [Software] [Press]

(4) Gurnis, M., et al., including Idini, B. (2019). Incipient subduction at the contact with stretched continental crust: The Puysegur Trench, Earth and Planetary Science Letters

(3) Leyton, F., Pastén, C., Ruiz, S., Idini, B., & Rojas, F. (2018). Empirical site classification of CSN network using strong‐motion records. Seismological Research Letters.

(2) Luo, Y., Ampuero, J. P., Galvez, P., Van den Ende, M., & Idini, B. (2017). QDYN: a Quasi-DYNamic earthquake simulator (v1. 1). Zenodo.
[Software]

(1) Idini, B., Rojas, F., Ruiz, S., & Pastén C. (2017). Ground motion prediction equations for the Chilean subduction zone, Bulletin of Earthquake Engineering.