Earthquake statistics changed by typhoon-driven erosion

Area of Science:

• Earth Science
• Geology
• Geophysics

Background:

• Earth's surface topography evolves due to tectonic and climate-driven processes.
• The influence of topographic change on lithospheric deformation is known, but the scale of this feedback is unclear.
• Previous research has not established a direct link between single weather-driven erosion events and tectonic activity.

Purpose of the Study:

• To investigate the impact of a single, extreme weather-driven erosion event on tectonic activity.
• To determine if surface processes can influence lithospheric deformation at a small scale.
• To provide evidence for the feedback between surface erosion and tectonics.

Main Methods:

• Analysis of seismic data following Typhoon Morakot in southern Taiwan (2009).
• Quantification of landslide and erosion extent caused by extreme precipitation.
• Comparison of earthquake frequency and magnitude scaling before and after the erosion event.

Main Results:

• Typhoon Morakot caused exceptional landsliding and erosion in southern Taiwan.
• A significant increase in shallow earthquake frequency (depth < 15 km) was observed for at least 2.5 years post-event.
• Earthquake magnitude-frequency scaling changed abruptly in areas of intense mass wasting.

Conclusions:

• Progressive removal of landslide debris by rivers increased crustal stress rates.
• This increase in stress rate demonstrably affected earthquake activity.
• This study provides the first evidence linking a single weather-driven erosion event to tectonic effects.