As humanity's exploration of the Earth's internal structure deepens, Earth's free oscillations, serving as crucial "fingerprints" for revealing the large-scale structure and dynamic processes within the Earth, have always been a core subject in geophysics. Ground-based station observations are currently the mainstream method for measuring Earth's free oscillations. With the advancement of space technology, high-precision inter-satellite distance measurement holds the potential to become a novel method for detecting these oscillations.

In a recent paper published in Space: Science & Technology, a research team from the School of Physics and Astronomy at Sun Yat-sen University, in collaboration with the TianQin Research Center for Gravitational Physics, proposed a novel detection and analysis method for Earth's free oscillations utilizing the "TianQin" space-borne gravitational wave detector. The study constructed a theoretical response model for Earth's free oscillations within the TianQin detector and derived their analytical waveform for high-orbit satellite laser interferometric measurements. Through numerical simulation and Bayesian parameter estimation, the research team demonstrated that for a major seismic event like the 2008 Wenchuan earthquake, TianQin could achieve a clear detection with a signal-to-noise ratio as high as 73 and independently distinguish at least nine different free oscillation modes.

Kyoto, Japan -- Mangrove forests are natural wonders that protect coastal areas, particularly in tropical and subtropical regions. They are able to dissipate wave energy and limit flooding, which can even mitigate tsunamis and coastal inundations during tropical cyclones. For this reason, mangroves are attracting attention as Nature-based Solutions, or NbS: natural infrastructure with the potential to enhance coastal resilience in an environmentally friendly way.

As climate change is altering ocean conditions and intensifying storms, many coastal communities face growing risks from flooding and extreme wave events; hence mangroves can serve to both mitigate disasters and help communities adapt to climate change. However, these forests remain underutilized in engineering applications due to a limited understanding of how they interact with hydrodynamic forces. Accurately modeling their complex root structures, known as prop-roots, while quantifying their wave attenuation effects has posed a particular challenge.

A collaborative team of researchers from Kyoto University's Disaster Prevention Research Institute resolved to address this knowledge gap. "Japan has a long history of using pine trees for coastal defense, and we want to apply this knowledge to mangroves to develop smart, cost-effective disaster risk reduction," says first author Yu-Lin Tsai.