Developing the first 3D velocity structure model for the Macquire Ridge Complex

By collaborating with researchers from University of Cambridge, California Institute of Technology, Nanyang Technological University, University of Maine, University of Tasmania and Woods Hole Oceanographic Institution, we develop the first 3D seismic velocity model for the lithosphere of the Macquire Ridge Complex (MRC). MRC evolved from a spreading mid-ocean ridge and is dominated by a transpressional plate boundary. This unique ridge is composed entirely of oceanic crust and upper mantle rocks and has the most significant underwater strike-slip events on the planet occurring in the region, and the grand question of the possibility of incipient subduction, studying the deep structures in this region will not only be beneficial to the tsunami disaster mitigation and prevention for the Australian coast but only contribute to the understanding of the evolution of the solid Earth.

This study is the first journal contribution from research on the waveform dataset recorded by a temporary network of ocean-bottom seismometers (OBSs) our team deployed in the Furious Fifties near Macquarie Island during 2020–2021. Our study uses full-waveform ambient noise tomography to develop a 3-D S-wave velocity model for the crust and uppermost mantle of the central Macquarie Ridge Complex. To date, attempts to use a model that includes a water layer to undertake full waveform tomography are rare. It is one of the pioneering full-waveform inversion papers that includes a water layer. It is also a pioneering attempt to study the 3-D S-wave velocity structure of the crust and uppermost mantle along the entire ~1500-km-long MRC.

Our analysis reveals prominent high S-wave velocity anomalies along the central Macquarie segment. These high S-wave velocity anomalies may suggest the presence and distribution of deep-seated upper mantle rock in the crust, indicating that the lithosphere in this region has not been substantially reworked during obduction and incorporation within an orogenic belt.

Developing the first Lg-wave attenuation model for the crust of the whole Australian continent

We use Lg-waves recorded on vertical components by seismic stations deployed across and around the Australian continent to construct a high-resolution seismic attenuation model for the entire Australian crust, across multiple frequency bands. This crustal attenuation model not only offers an innovative approach to simulating high-frequency ground motion generated by earthquakes anywhere on the Australian continent, which has significant meaning for the construction of low-rise buildings, but it also addresses a long-standing geological question regarding the existence of the Tasman Line—an important feature tied to the formation mechanisms of the Australian continent. Our new model reveals a clear boundary between the eastern and western parts of the Australian continent, thereby confirming the existence of the Tasman Line and providing valuable insights into the ongoing evolution of Australia in response to tectonic plate movements

Exploring the uppermost mantle structure of the Australian continent

We use a large dataset of Sn-wave traveltimes to perform a tomographic inversion of the 3D velocity structure in the uppermost mantle beneath the entire Australian continent. To address the challenge of inaccurate travel-time picking caused by the influence of P-coda waves, we develop and apply an innovative method for reliably identifying the onsets of Sn waves in this research. Based on this high-resolution S-wave velocity model, we identify several regions of extremely low wave speed along the entire eastern coastline, which may indicate remnants of a mantle plume in the uppermost mantle. These low-velocity anomalies are closely associated with the distribution of volcanoes along the coast, providing valuable insights into the geological evolution of the Australian continent.

The Lunar seismology: new missions

I'm currently working on the Lunar seismology: new missions; subcontract with Fleet Space Technologies Moon to Mars: Demonstrator program funded by the Australian Space Agency (https://fleetspace.com/news/fleet-space-awarded-a4m-demonstrator-program-contract-to-harness-seismic-data-at-moons-south-pole). I'm developing an innovative new tomographic method based on coda-correlation wavefields to study the interior of planets. This method is particularly applicable to the Moon, where seismic deployments are extremely limited. It will contribute to the most detailed understanding of the Moon's structure to date. 

Nuclear explosion monitoring

I'm currenlty working on nuclear explosion monitoring. One project is "Improving capabilities to detect, locate, discriminate and characterize the depths, yields and other emplacement conditions of nuclear explosions" funded by U.S. Air Force Research Laboratory (DoD/AFRL); the other is "Post-Certification Activities of PS02 and IS07, Warramunga, Australia" funded by the United Nations Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization. 

We deploy seismic stations in the centre of the Northern Territory.  These stations will be used to detect tremors from underground nuclear testing, as well as infrasound waves from atmospheric nuclear detonations. The data collected from these stations will also contribute to the exploration of Earth's core. In these projects, I am working on source mechanism inversion using a Bayesian inversion scheme. We are striving to address the impact of noise on the original datasets. This work will significantly enhance global monitoring of nuclear explosions.