Changes in water levels beneath the Earth’s surface, driven by glacier snowmelt and rainfall, are triggering a surge in microearthquakes in New Zealand’s central Southern Alps. This revelation comes from a study led by The Australian National University (ANU) and published in the journal Geochemistry, Geophysics, Geosystems.
The research highlights a seasonal pattern where the frequency of these small, often imperceptible earthquakes increases during the warmer spring and summer months. As temperatures rise, meltwater from glaciers and seasonal snow descends from high elevations, infiltrating the “highly fragmented” mountain bedrock, according to Dr. Konstantinos Michailos, the study’s lead author.
Understanding the Seasonal Seismicity
The Southern Alps, an active mountain range featuring nearly all of New Zealand’s glaciers, is susceptible to extreme weather, including intense rainfall. Dr. Michailos notes that the region can receive over 300 millimeters of rain in just three days. This combination of seasonal snowmelt and heavy rainfall elevates groundwater levels, increasing pore-fluid pressure in the crust and potentially triggering frequent microquakes.
“Our findings highlight the role of extreme rainfall and glacier dynamics in triggering shallow earthquakes and could provide scientists with a better understanding of the potential drivers of seismic activity in other alpine regions around the world,” said Dr. Michailos.
Seismic Activity and Climate Change
New Zealand’s central Southern Alps lie adjacent to the Alpine Fault, the South Island’s most significant seismic hazard. The study found that shallow-depth earthquakes, occurring at depths between three to six kilometers below sea level, were more frequent during spring and summer. These events were most common near glacier terminals, particularly around the Murchison Glacier.
“We found that a lot of these earthquakes were happening within hours or a day after large rainfall events there—a pattern also documented in other parts of the world such as the European Alps,” Dr. Michailos explained.
The study underscores the impact of human-induced climate change, which has led to the shrinking of the central Southern Alps’ glaciers in recent decades. This glacial mass loss, coupled with seasonal snow fluctuations, redistributes stress in the Earth’s crust beyond what tectonic forces alone would cause.
Data Collection and Future Research
Since 2008, researchers have collected seismic data from an array of seismometers in the central Southern Alps, detecting over 8,000 microearthquakes from 2009 to 2020. The study focused on seismic activity near four major glaciers: Murchison, Tasman, Franz Josef, and Fox.
In October, the research team plans to return to the Southern Alps to deploy additional seismometers and gather more detailed seismic data. They will also install rainfall gauges and temperature sensors to complement existing local seismometers, enhancing their ability to record not only earthquakes but also landslides, avalanches, and rockfalls.
Collaborative Efforts and Broader Implications
This research is a collaborative effort involving scientists from ANU, New Zealand, and Switzerland. The findings could have broader implications for understanding seismic activity in other alpine regions worldwide, providing valuable insights into how climate change and extreme weather events influence seismicity.
More information: Konstantinos Michailos et al, Temporal Evolution of Seismicity in the Central Southern Alps, New Zealand: Evidence for Rainfall‐Triggered Seismicity, Geochemistry, Geophysics, Geosystems (2025). DOI: 10.1029/2025GC012317
As the research continues, scientists hope to unravel more about the intricate relationship between climate dynamics and seismic activity, potentially offering new strategies for predicting and mitigating earthquake risks in similar environments globally.
