3 May 2024–About six months before the 2023 Mw 7.8 Kahramanmaraş earthquake in Türkiye, transient short pulses of low-frequency seismic activity were occurring on the east side of the East Anatolian Fault Zone, researchers reported at SSA’s 2024 Annual Meeting.
Learning more about the properties and physical origins of these pulses could point toward a way of monitoring seismicity transients to improve intermediate-term (decadal) earthquake forecasting, the researchers note.
Zahra Zali of GFZ Potsdam and colleagues uncovered the pulses during their analysis of seismic catalog and waveform data collected by regional broadband stations in the months preceding the earthquake. The researchers found that there was an extended period of about eight months before the earthquake showing spatio-temporal clustering of seismic activity—a “preparation” signature that is similar to the stress evolution seen in laboratory studies of stick-slip faults.
From these data, Zali and colleagues used machine learning to extract spectral characteristics within the continuous seismic waveforms in low frequency (less than 5 hertz) recordings from nearby stations. Their analysis identified two main changes in spectral characteristics, occurring eight months and six months before the earthquake, and coinciding with elevated seismic rates.
In particular, the researchers found more than 3000 temporal seismic episodes, lasting between 12 and 30 minutes, each consisting of small transient pulses that resemble very small earthquakes. These episodes were only observed at five seismic stations that were within 46 kilometers of the future earthquake epicenter, and began six months before the mainshock. The investigation of the tectonic or anthropogenic origin of these pulses involves various analyses, which will be discussed in the presentation.