For more than a decade, a research team in Xian, China, has devoted itself to studying potential precursors to earthquakes. They are spearheaded by Zhang Maosheng, a professor and dean at Xian Jiaotong University in Shaanxi province and a researcher for China’s Ministry of Natural Resources. The team has been diligently monitoring and analyzing seismic data, hoping to bring humanity closer to accurate earthquake predictions. Their long-term vision is a global network of gravimeter machines which would allow researchers worldwide to collaborate on data collection and provide extensive coverage.
Their efforts caught global attention when, on July 16, an earthquake of 7.2 magnitude struck off the Alaska Peninsula. Interestingly, 84 hours before the seismic event, the Xian research team registered an abnormal data reading, signifying a major earthquake was imminent. Unfortunately, they could not determine when or where this earthquake would occur.
Zhang and his team are accustomed to this situation. Over a decade of data observation has familiarized them with the frustrating reality of knowing an earthquake is on the horizon, but lacking sufficient information to issue a warning. However, they remain hopeful that their research will eventually make full earthquake prediction a reality.
Published in the Chinese journal Northwestern Geology in June, their paper reveals that they have been tirelessly examining potential earthquake precursors for more than a decade. Utilizing high-precision gravimeters, the team has managed to collect data from dozens of earthquakes since 2010, including the catastrophic Turkey-Syria earthquake on February 6.
The paper introduces a groundbreaking concept: monitoring the Earth’s gravitational field at low frequencies to potentially predict high-magnitude, imminent earthquakes. These precursors are abnormal phenomena that precede earthquakes, such as smaller earthquake clusters or unusual animal activity, according to the United States Geological Survey (USGS).
During their data observation, the team noticed a possible precursor and a potential four-phase mechanism for short-impending earthquakes. Notably, during the second phase, dubbed the “locked energy storage” phase, anomalies in dynamic gravity appear as peaks in gravity readings. This phase generally occurs between 1 and 15 days prior to an earthquake.
These abnormalities were observed using a gravimeter, an instrument typically employed to measure changes in Earth’s absolute gravity. To optimize their findings, the team devised their own dynamic gravimeter that leverages liquid suspension to detect abnormalities based on liquid motion. This proved to be not only more accurate for short-term earthquake prediction but also more cost-effective and portable.
This new method provided astonishing results. An anomalous reading was recorded 83 hours prior to a 7.4 magnitude earthquake in Sulawesi, Indonesia, in September 2018, and 116 hours before a 7.2 magnitude earthquake in Tajikistan in February.
While the team noted that these gravity peaks did indicate an impending earthquake within a short timeframe, and the peak strength could imply the magnitude, they were still unable to pinpoint the exact time and location scientifically. The USGS maintains that accurate earthquake predictions necessitate precise details on time, location, and magnitude. To date, no scientist has successfully predicted a major earthquake.
Nonetheless, Zhang’s research team has consistently detected signs of major earthquakes days before their occurrence. In fact, Zhang claims that for earthquakes above magnitude 7, their prediction accuracy is 100%. For these high-magnitude earthquakes, the occurrence of a peak is invariably followed by an earthquake, according to Liu Huaqing, a professor at Northwestern Polytechnical University in Xian and co-author of the paper.
The paper highlights that earthquake forecasting has been a priority for China since the 1950s. Successful forecasts in the 1970s helped reduce casualties. However, due to failures in predicting major earthquakes, many countries have moved away from earthquake prediction efforts. Despite the scepticism from scientists in countries like the United States and Japan, Liu disagrees with the prevailing view that earthquakes are unpredictable. He firmly believes that, at least for some earthquakes, accurate prediction is achievable.
Their pursuit of understanding dynamic gravity anomalies in relation to earthquakes isn’t government mandated. Instead, this group of dedicated researchers voluntarily undertook the study because they noticed a correlation between anomalous readings and seismic events.
The paper shares intriguing details like a log of group chat messages where an anomalous reading was noted five days before the Tajikistan earthquake, along with a forecast suggesting an earthquake could occur within three days. It also reveals an unprecedented observation during the February Turkey-Syria earthquake, where two anomalous peaks occurred consecutively. The team hadn’t seen this before and initially didn’t anticipate two separate earthquakes. However, when a magnitude 7.8 earthquake was succeeded by a 7.5 magnitude quake, they concluded that the double peaks corresponded to the two seismic events.
Reflecting on a decade of observations, Liu admitted that seeing large peaks and knowing a major earthquake was forthcoming had become almost routine for the team. They remain dedicated to their research, buoyed by their numerous findings and the potential global impact of their work.
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