A sequence of damaging earthquakes throughout the Asia Pacific region has raised worries among the public and the scientific community. Just on March 28, a magnitude-7.7 earthquake jolted Mandalay, Myanmar. This terrible disaster resulted in more than 3,600 deaths and subsequently resulted in incredible damage to the built environment. This intermediate depth earthquake was so powerful that its shaking was felt as far away as Bangkok, Thailand, over 1,000 km from the epicenter. Just days prior, a magnitude-6.7 quake hit off the South Island of New Zealand on March 25, contributing to heightened awareness of seismic risks.
Dr. Dee Ninis, a USGS seismologist, noted that seismic activity forecasts are subject to revision. These recent quakes appear to be completely unrelated and are more a response to the local tectonic forces that are at work. Even more importantly, he stressed, these events are typical of the broader pattern of seismic activity that we’re experiencing here at home and across the globe.
Understanding the Quake in Myanmar
Myanmar’s earthquake was an outlying classified as such because they happen so rarely. Dr Ninis explained that these kind of major quakes happen quite infrequently in this area.
“The Myanmar quake was an outlier because it’s in a much more infrequent class,” – Dee Ninis.
As he explained, the world averages about 18 big earthquakes a year. These very strong shocks are usually in the magnitude range of about 7 to 7.9. The reason, he explained, is that more powerful quakes produce aftershock sequences. The distance separating these latest earthquakes makes it clear that they are not aftershocks of the Myanmar quake.
“Larger-sized earthquakes often produce aftershocks — an increase in earthquake activity which can last for days, weeks, months, or years afterwards,” – Dee Ninis.
The Tectonic Forces at Play
Dr. Ninis clarified that earthquakes happen when the stress accumulates in the layers of the Earth’s crust. This stress is eventually released all at once, shaking the ground in the process. The recent quakes that struck in succession along the India-Australia plate boundary are a prime example of this phenomenon.
“When there is pressure built up in the crust, even a large earthquake may not be enough to release it,” – Dee Ninis.
This tectonic activity is not an outlier, it is part and a manifestation of trends of increasing seismic events at the global scale. Why earthquakes happen in clusters Dr. Ninis explains that earthquakes can happen in clusters due to the random nature of the earthquakes themselves. Those clusters are not evenly spaced out in time.
“But these earthquakes are not equally spaced out over any period of time; they often tend to cluster just as a result of their randomness,” – Dee Ninis.
Advancements in Seismology and Forecasting
Seismologists have made great advances in their ability to predict seismic activity. Dr. Kennett highlighted that while advancements in forecasting technology continue to improve, practical application of this information is essential for public safety.
Dr. Ninis stressed that even with all the innovation on forecasting, it’s very hard to predict specific events.
“Forecasts can change,” – Dee Ninis.
He noted that Australia experiences hundreds of smaller quakes annually. In the case of southeast Australia, it’s roughly 30 to 40 quakes a week!
“We typically experience 30-40 earthquakes per week [in south-east Australia], and maybe 15-20 of magnitude-3 to 3.9 every year,” – Dee Ninis.
Leave a Reply