Research

Our research group is dedicated to developing geophysics for improving the understanding of near-surface physical and mechanical processes and their spatio-temporal changes due to climate change.

Snapshots of our research in YouTube, click here, and permafrost YouTue

Current Projects:

Fiber-Optic For Environment SEnsEing (FORESEE) 

The physical properties of the Earth’s critical zone are likely to change as a function of space and time. However, physics of such changes is not well understood. The project aims to improve the understanding of these changes in near-surface environmental systems in a changing climate by collecting geophysical data using the underground telecommunication fiber-optic cables (Zhu & Stensrud, 2019; Zhu et al., 2021).

 

Geological CO2 Storage and Geothermal reservoirs

Geological CO2 storage is considered to be an effective method to reduce anthropogenic CO2 emission. Quantifying the dynamics of sequestered CO2 plumes is critical for safe long-term storage, providing guidance on plume extent, and detecting stratigraphic seal failure. The projects aim to develop seismic imaging methods for providing real-time information of CO2 plumes in the subsurface geological CO2 storage reservoirs (Zhu et al., 2019; Huang&Zhu, 2020). We explore how seismic velocity and attenuation properties respond to the CO2 porosity dynamics in the reservoir.

China's Yutu 2 rover, as seen by the Chang'e 4 lander on the far side of the moon.Shallow Geological Structure in other planets

Ground-penetrating radar (GPR) sends the radio pulse deep to the subsurface. A GPR transmitter and antenna emits electromagnetic energy into the ground. When the energy encounters a buried object or a boundary between materials having different permittivities, it may be reflected or refracted or scattered back to the surface.

Recent space missions including Chang’e 3/4 in the near-side and far-side moon used GPR to image the moon’s shallow structure. I am interested in uncovering the details of radar reflections to detect subsurface reflectors (Zhu et al., 2021).

Understanding seismic wave attenuation in rocks 

In past decades, seismic approaches based on the phase/traveltimes are widely and successfully used to image the subsurface geological structure. On the other hand, the amplitude of seismic waveform that is hoping for providing more physical information about rocks has not been explored in a consistent way. There exists a gap between current seismic capability and the full physics of seismic waveform. For example, as Earth media always attenuate seismic waves during propagation seismic data includes attenuation effects that contributes seismic amplitude seriously. To fill this gap, we have to deal with seismic attenuation (intrinsic and scattering) physically and practically in seismic techniques (Zhu&Harris, 2014; Zhu&Carcione, 2014; Zhu, 2017).

Past Projects:

Induced seismicity using pass source imaging and tracking

Using time invariance and reciprocity properties of wave equations, time-reversal (TR) algorithms are able to retrace the recorded wave propagation path back through the medium and converge on the location of initial sources. The robustness and simplicity of time-reversal techniques make them effective tools for resolving source localization problems in numerous physical fields including seismology, land-mine detection, non-destructive detection and acoustics.

When intrinsic attenuation is considered in the Earth, however, wave equations are no longer time-invariant under time-reversal. As a result, time-reversed waves that are back-propagated into such a medium under the same conditions as in a non-attenuating medium lose the property of symmetry in time. The complication of time variance can be addressed by an appropriate compensation for the intrinsic attenuation applied to the backward-propagated wavefields during TR propagation. [see Zhu, GJI, 2014Zhu, Geophysics, 2015]

High resolution seismic reflection imaging by reverse-time migration with attenuation compensation

Attenuation always reduce amplitudes and distort the phase of seismic waves. When back propagating such a seismic data (a step for seismic imaging), seismic imaging will result in a dimmed image with incorrect amplitude and phase, especially in the areas of high attenuation, e.g., the gas chimneys. To address this problem, I proposed a compensated strategy for time-reversal imaging and Q-RTM to mitigate attenuation effects in time-reversal source image and RTM image, respectively. The method has been successfully tested in synthetic data and field data. [see Zhu et al., Geophysics, 2014; Zhu and Harris, Geophysics, 2015b; Zhu and Sun, Geophysics, 2017]