Volcanologists dedicate their efforts to monitoring volcanoes, striving to predict potential eruptions accurately. The primary challenge lies in determining both the likelihood and exact timing of an eruption.
To tackle this issue, a team of researchers created an innovative early detection system designed to issue timely warnings about volcanic eruptions. Their key motivation was to improve upon previous warning systems, which often missed critical underground volcanic activities occurring just before an eruption.
Between 2014 and 2023, researchers carried out extensive tests to effectively identify transient low-frequency oscillations using a seismograph. The focus on these transient signals is crucial since they stem from earthquakes and other surface-related phenomena, which scientists utilize to predict volcanic eruptions. These include ground tilting caused by magma movement and volcanic gases. Scientists refer to these as “jerk” signals due to the sudden movements they represent.
The team conducted their experiments at Piton de la Fournaise, located on La Réunion Island off the southeast coast of Madagascar. They identified the jerk signal by analyzing short-term signals in existing experimental seismic data. During a live experiment, they detected a significant signal 8 kilometers (about 5 miles) from the volcano at the Rivière de l’Est seismic observatory. These signals indicated height changes on the surface as magma migrated, often appearing mere minutes to hours before an eruption.
Researchers measured the jerk signals in Newton meters per second, which reveals the velocity of physical changes occurring in or around the volcano. Alongside real-time experiments, they analyzed historical data to verify the accuracy of jerk signals and determine their occurrence just before eruptions.
To avoid false alarms, the research team distinguished between ocean tidal signals and transient jerk signals using advanced computational software. This step was necessary as ground-recording instruments are also sensitive to tidal movements.
The Jerk system issued its first automated warning in June 2014, alerting authorities an hour before the initial volcanic tremor, signaling that magma was nearing the surface. The last signal recorded in their study occurred on July 2, 2023, just 40 minutes prior to an eruption at a slow rate of 1.5 Newton meters per second. Throughout 2014 to 2023, jerk detections occurred anywhere from minutes to eight hours before an eruption.
To measure the reliability of the jerk signal, the team reviewed historical eruption records at Piton de la Fournaise. They established that for 24 eruptions between 1998 and 2010, jerk alarms would have activated 83% of the time. From 48 eruptions between 1998 and 2023, including those during real-time testing, approximately 42 jerk warnings would have been issued. Real-time analysis also revealed that the jerk signal’s accuracy has improved compared to eruptions from two decades ago.
While the research team successfully identified pre-eruption signals, they noted that data processing requires at least 10-15 minutes, sometimes leading to delayed alarms. They reported two instances of late warnings: one on June 11, 2019, and another on February 10, 2020. After a decade of monitoring jerk signals, the team evaluated alarm success rates for 22 out of 24 eruptions, achieving a positivity rate of 92%.
Prior to the introduction of jerk signals, many volcanologists struggled to predict the exact moment of an eruption. The research team concluded that, alongside traditional methods of detecting pre-eruption earthquakes, scientists can now effectively use jerk signals to alert authorities, thereby improving safety for communities living near volcanoes worldwide.
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Source: sciworthy.com
