Geophysical Journal International

SummarySolving the wave equation is essential to seismic imaging and inversion. The numerical solution of the Helmholtz equation, fundamental to this process, often encounters significant computational and memory challenges. We propose an innovative frequency-domain scattered wavefield modeling method employing neural operators adaptable to diverse seismic velocities. The source location and frequency information are embedded within the input background wavefield, enhancing the neural operator’s ability to process source configurations effectively. In addition, we utilize a single reference frequency strategy, which enables scaling from larger-domain forward modeling to higher-frequency scenarios, thereby improving our method’s accuracy and generalization capabilities for larger-domain applications. Several tests on the OpenFWI datasets and realistic velocity models validate the accuracy and efficacy of our method as a surrogate model, demonstrating its potential to address the computational and memory limitations of numerical methods.

SummaryThe response of well water temperature to earthquakes is crucial for understanding subsurface seismic fluid dynamics. However, recent studies have primarily focused on observations at a single depth and have employed single-aquifer models, which may lead to controversies when explaining fluid flow. In this study, we develop single- and double-aquifer models to estimate well-water temperature variations at different depths in response to changes in pore pressure, permeability, and aquifer recharge temperature. The results indicate that variations in aquifer pore pressure and permeability result in significant differences in vertical flow velocity and temperature changes at various depths. When the borehole bottom is impermeable, for a single aquifer, temperature variation is maximal above the aquifer and variable at the aquifer depth, but nearly zero below the aquifer; for two aquifers, different pore pressure and permeability changes in each aquifer produce distinct temperature variation patterns, with minimal temperature change below the lower aquifer. If the borehole bottom is permeable, temperature variation becomes obvious below the lower aquifer. When cold or hot water from the aquifers flows into the borehole, significant temperature perturbations remain confined within a few metres of the aquifer within one day. Finally, a field case study investigates the co-seismic water temperature responses at three depths in the Chuan No. 03 well, triggered by the 2008 Mw 7.9 Wenchuan earthquake. The double-aquifer model effectively explains the complex co-seismic temperature fluctuations at different depths. Observation at a single depth risk missing crucial information, and multi-depth temperature observation is a promising approach for interpreting and monitoring groundwater responses to earthquakes.