Haenam Earthquake Interim Results: "Large-Scale Earthquake Unlikely"

The earthquake occurrence distribution in the Haenam area is shown with past earthquakes (blue), recent earthquakes (red), and earthquake observation stations (triangles).

[Asia Economy Reporter Junho Hwang] Although a total of 71 earthquakes, including a magnitude 3.2 earthquake, have occurred this year in Haenam, Jeollanam-do?a region previously considered a seismic calm zone?research results indicate that the likelihood of these events leading to a major earthquake is low. The Korea Institute of Geoscience and Mineral Resources announced on the 14th the interim investigation results of the Haenam earthquakes (including the magnitude 3.2 earthquake on May 3) that have occurred intensively since April 26.

Low Possibility of a Major Earthquake

Epicenter Area Surface Geological Survey Location Map

The institute analyzed that the Haenam earthquakes are unlikely to lead to a major earthquake.

First, the research team analyzed the earthquake occurrence history in the Haenam-gun area over the past 20 years and evaluated that the frequency is low, with an average of 6.5 earthquakes per year (a total of 133 events). Most of the earthquakes that occurred were related to blasting activities in surface mines. Pure fault-type earthquake occurrences are very rare.

With cooperation from the Korea Meteorological Administration, seismic data from a total of 11 observation stations were analyzed, which also lowered the possibility of a major earthquake. Regarding the Haenam earthquake that occurred at 22:07 on May 3, the focal depth was about 20.5 km, and the earthquake fault was analyzed as a strike-slip fault with a strike of 99˚ and a dip of 52˚. This means it is a fault where two blocks move horizontally in parallel with the strike direction. Additionally, the waveforms of the 71 seismic movements since April 26 showed high correlation with the waveform of the Haenam earthquake, and the distribution of epicenters was similar to the Haenam earthquake in the west-northwest to east-southeast direction.

Final Investigation Results to be Announced in the Second Half of the Year

Fault zone of outcrop scale in the northwest-west to southeast-east direction

The research team also confirmed through field geological surveys that the Haenam earthquake was caused by a seismic fault in the west-northwest to east-southeast direction. Through three geological surveys, they identified a medium- to small-scale fault group in the west-northwest to east-southeast direction across the entire epicenter area. Analysis of outcrop-scale faults at 11 locations revealed a fault group dipping steeply (60°~90°) in the northwest-southeast to west-northwest?east-southeast direction (N30°~80°W). Furthermore, analysis of 134 fractures at about 30 locations showed that fractures in the northwest-southeast and west-northwest?east-southeast directions were most dominant.

Gravity measurements at 363 points near the epicenter revealed a distinct east-west trending gravity anomaly linear structure along the boundary between Precambrian granite and Cretaceous tuff in the southern part of Samho-eup, Yeongam-gun. The research team plans to precisely confirm the existence of the fault through future MT surveys or seismic wave surveys.

Gi Won-seo, head of the Haenam Earthquake Task Force, stated, "We conducted a comprehensive analysis of the unusually frequent Haenam earthquakes by combining seismic analysis with field geological surveys and geophysical explorations," adding, "We will strive to provide the public with more scientific and objective data on the causes of the Haenam earthquakes and the characteristics of crustal activity by incorporating the results of upcoming geophysical surveys."

The institute plans to announce the final research results on the Haenam earthquakes in the second half of this year, applying the latest geophysical survey research technologies.

This content was produced with the assistance of AI translation services.