They might not be bluffing. The announcement followed a 5.1 magnitude earthquake near the same location as a 2013 nuclear test. International officials have expressed doubt over the North’s ability to create a true hydrogen bomb but state television said the act of “self defense” was real. The U.S. says it will send “sniffer” planes over the region to evaluate. South Korea held an emergency meeting after the report and Japanese officials scheduled their own talks for later in the day. Experts say the test could stress relations with China, one of Pyongyang’s rare allies.