Earthquake epicenter map in South Korea Jan 1978 - Dec 1999 / <a rel="nofollow" class="external free" href="http://www.kma.go.kr/communication/webzine/earthquake/eq_obser_1978_2000.pdf">http://www.kma.go.kr/communication/webzine/earthquake/eq_obser_1978_2000.pdf</a> - I refer to this PDF file of Korea Meteorological Administration during making this map
<div class="fn value">
OpenStreetMap contributors</div>
CC BY-SA 3.0
<a rel="nofollow" class="external text" href="https://www.openstreetmap.org">openstreetmap.org</a>