Urban and dense array seismology
A paucity of suitable equipment has seriously limited our understanding of the Earth’s structure and tectonics in South East Asia. Now, however, seismic nodal instruments are revolutionizing the acquisition of low-cost, high-quality seismic data in industry and academia. The instruments facilitate the acquisition of large, dense, seismic surveys in any land environment which can address many geoscience challenges faced by SE Asia. We propose two principle applications of seismic nodal arrays:
1. To guide smart city development and
2. To address fundamental scientific questions regarding regional tectonics
Smart cities strive to ensure economic and environmental stability while improving the urban environment. Singapore faces particular challenges due to its limited land area and lack of natural resources; as a result, increased development of the subsurface will form a crucial part of Singapore’s future. Seismic imaging can provide the essential knowledge key to understanding subsurface systems for the management of resources, mitigation of geohazards, and infrastructure design. Furthermore, SE Asia is one of the most seismically active areas of the world, and this severely impacts its societies and economies. The Sumatran Fault, one of the world’s largest strike-slip faults, poses a serious hazard to Sumatra’s 50 million people. High-resolution imaging of the Earth’s structure here can address key questions about how this fault behaves, and its relationship with regional tectonics.
With 200 short-period seismic nodes we purchased in 2018, we deployed 88 of them throughout Singapore from March to April 2019, which is the first time of this kind in Singapore. The dataset has been used to image the detailed crustal thickness through receiver function analysis (Lythgoe et al., 2020). This work shows the feasibility to conduct a high-resolution waveform seismology study in a noisy urban environment, which was rarely attempted in other megacities. Using ambient noise cross-correlation and surface wave tomography, our dataset reveals that the shallow (~1km) velocity structure in Singapore has good agreement with the geological units, i.e., our tomography model shows fast shear wave speed in central Singapore that is mostly granite and low shear wave speed in eastern Singapore that is mostly Quaternary sediment (Lythgoe et al., 2021). Our dataset also reveals daily fluctuation of the traffic noise, blasting activities, and more interestingly the acoustic signals from the thunders (Lythgoe et al., 2021). In the future, seismic node deployment could be combined with Distributed Acoustic Sensing (DAS) techniques to take advantage of dense dark fibres in Singapore to construct even denser and higher resolution modern seismic networks, which will better serve a smart city.
- Earth Observatory of Singapore
- Thermal squeezing of the seismogenic zone controlled rupture of the volcano-rooted Flores Thrust. Science Advances. 7(5), (2021).
- Large-scale crustal structure beneath Singapore using receiver functions from a dense urban nodal array. Geophysical Research Letters. 47(7), (2020).