Distributed acoustic sensing system utilizing Gaussian-shaped probe pulses for seismic wave detection

Distributed acoustic sensing (DAS) technology, with enhanced low-frequency detection capabilities, is increasingly crucial for applications such as seismic monitoring and urban subsurface structure imaging. This study developed a DAS engineering prototype with excellent low-frequency (0.01-1 Hz) response. We demonstrate that employing Gaussian-shaped probe pulses, in place of conventional square-wave pulses, can significantly suppress instrument noise floor across the entire frequency range, especially achieving superior sensing performance in the low-frequency range. Laboratory measurements achieved a self-noise level of less than -156.8 dB re ε/√Hz @ 0.1 Hz with a 4 m gauge length over a 5 km sensing distance, representing a 32-dB reduction compared with using rectangular probe pulses. The system successfully reconstructed a 0.01 Hz piezoelectric vibration signal at a 5 km sensing distance and maintained a consistent amplitude-frequency response from 0.01 Hz to 4 kHz. Field deployments further validated its low-frequency performance. The DAS instrument successfully detected low-frequency seismic signals, including a MW 7.3 earthquake (0.02-0.09 Hz) occurring 1570 km away in Hualien County, China, and a MW 6.6 deep earthquake (0.02-0.13 Hz) occurring 2036 km away in Manila, Philippines. These results demonstrate the low-frequency performance of the developed system, highlighting its substantial potentials for earthquake monitoring, hydroacoustic sensing, and near-surface imaging.