Seismic background noise dramatically decreased as a result of lockdown measures in place for mitigating the spread of COVID-19.

Seismic noise with frequencies above 1 Hz is often called “cultural noise” and is generally correlated quite well with human activities. Recently, cities in mainland China and Italy imposed restrictions on travel and day‐to‐day activity in response to COVID‐19, which gave us an unprecedented opportunity to study the relationship between seismic noise above 1 Hz and human activities. Using seismic records from stations in China and Italy, we show that seismic noise above 1 Hz was primarily generated by the local transportation systems. The lockdown of the cities and the imposition of travel restrictions led to an $∼4–12dB$ decrease in seismic noise power in mainland China. Data also show that different Chinese cities experienced distinct periods of diminished cultural noise, related to differences in local response to the epidemic. In contrast, there was only $∼1–6dB$ decrease of seismic noise power in Italy, after the country was put under a lockdown. The noise data indicate that traffic flow did not decrease as much in Italy and show how different cities reacted distinctly to the lockdown conditions.

Underwater Distributed Acoustic Sensing (DAS) utilizes optical fiber as a continuous sensor array. It enables high‐resolution data collection over long distances and holds promise to enhance tsunami early warning capabilities. This research focuses on detecting infragravity and tsunami waves associated with earthquakes and understanding their origin and dispersion characteristics through frequency‐wavenumber domain transformations and beamforming techniques. We propose a velocity correction method based on adjusting the apparent channel spacing according to water depth to overcome the challenge of detecting long‐wavelength and long‐period tsunami signals. Experimental results demonstrate the successful retrieval of infragravity and tsunami waves using a subsea optical fiber in offshore Oregon. These findings underscore the potential of DAS technology to complement existing infragravity waves detection systems, enhance preparedness, and improve response efforts in coastal communities. Further research and development in this field are crucial to fully utilize the capabilities of DAS for enhanced tsunami monitoring and warning systems.

The 28 March 2025 Mw 7.7 Myanmar earthquake on the Sagaing fault caused widespread building collapses and over 3800 fatalities, as well as strong shaking in Bangkok. High-frequency backprojection very early on revealed an ∼500 km rupture. Following a bilateral subshear propagation, the rupture accelerated southward to at least 5.3 km/s, reaching the stable supershear regime, as also confirmed by Mach-cone analysis with Love waves. Pixel tracking analysis from optical and radar imagery confirms the rupture length and indicates a peak surface offset of 5 m and average offsets of 3–4 m along the rupture zone. Pseudodynamic rupture inversion constrained by seismic waveforms and the radar-interferometric deformation field indicates ∼4 m slip over ∼15 km depth range. The earthquake yielded unusually few aftershocks; its supershear rupture likely released most of the accumulated stress. It appears that the rupture almost certainly broke the Sagaing gap and very likely overlapped completely with the 1956 M 7.0 event. It may also have partially overlapped with the 1946 M 7.8 rupture zone in the north and the 1930 M 7.5 event in the south. Acceleration to supershear only started in the gap area, and the rupture decelerated and arrested after moving into the previously broken segment.

Using continuous data from a dense seismic array in Southwestern China, we tracked S‐wave microseism sources generated by two storms in Southeast Australia and the North Atlantic. In the frequency band 0.1–0.2 Hz, the beam strengths for SV‐ and SH‐wave sources can reach 29% and 18% of P‐wave, respectively. We found that the strong SH‐wave is only observed when the seismic sources are near the thick sedimentary regions whereas P‐ and SV‐wave is irrespective of that. It appears that in addition to a three‐dimensional structure that is needed for conversion from P‐wave to SH‐wave, amplitude enhancement by a sedimentary layer is essential for the detection of SH‐wave.