Host: Patty Pei-Ying Lin

Tea time will be hosted after the talk

Understanding the role of aseismic slip in earthquake cycles is essential for assessing seismic hazards and short-term forecasting. Eastern Taiwan’s double-vergence suture zone, where the Philippine Sea Plate subducts beneath the Eurasian Plate, experiences frequent M ≥ 6 earthquakes and widespread aseismic slip, making it an ideal natural setting to study earthquake triggering processes. Using a 24-year catalog of repeating earthquake sequences (RESs) and earthquake swarms, we investigated aseismic deformation leading up to the April 3, 2024 Mw7.3 Hualien earthquake. We find that nine out of ten swarms in the epicentral area, northern Longitudinal Valley, were accompanied by increasing aseismic slip rates, as revealed by RESs on the west-dipping Central Range Fault (CRF). A notable aseismic slip episode in 2021, indicated by GNSS signals, the accelerated RES-derived slip rate, and a four-month-long swarm sequence with high diffusivity (~5.2 m²/s), suggests joint contributions from over-pressured fluids and deep fault creep. This episode was followed by a cluster of M6+ events and a later phase of slightly accelerating seismic and aseismic activity beginning in 2023. Coulomb stress modeling indicates that these aseismic slip events and transient fluid flow increased stress on the CRF, potentially promoting the 2024 mainshock. Our results provide rare evidence for aseismic-slip-induced stress triggering of a major earthquake and highlight the importance of integrating aseismic processes into earthquake hazard models for collisional fault systems.

Host: Kate Hui-Hsuan Chen

Feedback from massive stars is one of the greatest sources of energy and momentum in the interstellar medium (ISM). Ionizing radiation, stellar winds and supernovae collectively shape the molecular clouds, the birthplace of stars, as well as their host galaxies. They play a significant role in regulating the entire star formation process.

In this colloquium, I will provide an overview of how feedback interacts with the ISM, and how astrophysicists examine their impact using state-of-the-art computational simulations. Specifically, I will discuss why the highly-asymmetrical nature of supernova remnants may impose a problem to our current feedback models. I will demonstrate that supernovae could actually induce a higher dynamical impact to its local ISM than what was previously expected. 

ES-CAG joint colloquium

Host: Yueh-Ning Lee

Host: Patty Pei-Ying Lin

Host: Ting-Kuang Yeh

Recognizing soil moisture regimes provides a fundamental framework for understanding hydroclimate dynamics. The relationship between soil moisture and evapotranspiration is inherently nonlinear, with dry, transitional, and wet regimes defined by whether land-surface fluxes are limited primarily by water availability or by energy. These regimes play a central role in regulating how the land surface modulates climate variability and extremes. The rapidly expanding availability of daily records of soil moisture, surface heat fluxes, and near-surface atmospheric states has enabled the development of data-driven approaches to track soil moisture regimes. Through the recognition of soil moisture regimes, substantial progress has been made in understanding land–climate interactions, hydroclimate change, and associated dry-hot extremes in past few years.

In this talk, I will discuss: (1) recent approaches for diagnosing soil moisture regimes and the associated metrics derived from these diagnostics; (2) how soil moisture regimes, and their control on evapotranspiration, shape historically significant compound hot–dry extreme events; (3) a new empirical framework that bypasses explicit soil moisture regime classification to interpret changes in historical evapotranspiration; and (4) my perspectives on future research directions related to soil moisture regimes and changing evapotranspiration.

Host: Cheng-Ta Chen

Host: Wei-Ling Tseng

Host: Cheng-Ta Chen