Today marks the one-month anniversary of the massive earthquake and tsunami that decimated Japan's northeast coast and started the ongoing Fukushima nuclear crisis. But while rattled residents mourned their losses and looked toward the future and rebuilding, a sharp aftershock once again shook the Sendai region, causing panic and alarm, but no injuries or deaths.

The quake, which various reporting agencies have put between 6.6 and 7.1, hit at 5:16 p.m., local time, exactly three-and-a-half hours after ceremonies at 2:46 p.m. to acknowledge the passage of one month since the 9.0 quake and tsunami that killed at least 25,000 people. It threatened, but ultimately did not derail, ongoing attempts to control damaged reactors at the Fukushima nuclear plant, according to the New York Times.

An official for the operator of the Fukushima plant, Tokyo Electric Power Company, said a temporary loss of external power at the plant following the aftershock had briefly knocked out pumps sending water into the facility’s three most severely damaged reactors.

But the most damaging effect of today's tremblor was psychological, not physical. Aftershocks have rocked Japan regularly for the past month, including a 7.1 jolt last Thursday that disrupted repairs at Fukushima. According to the Associated Press, "people in a large electronics store in Sendai screamed and ran outside and mothers grabbed their children," when today's quake hit. That panic is something that wouldn't have happened before last month's disaster. Earthquakes the size of today's hit Japan often, and before last month they rarely caused much disruption.

In a Newsweek article yesterday, George A. Bonanno asked how much trauma the Japanese people could handle, and came to the conclusion that they (and all of us) can take a lot of lumps, but not if the government doesn't provide a full account of the facts. In addition, he pointed out that the problem with the current crisis is, "it doesn't seem to want to end." He was referring to the nuclear crisis, but the same is true for the fault-line action. It's hard to recover from a state of shock when aftershocks pervade.