An anomalous pair - the westernmost (left) was a Richter 5.9 on 9/22/1960.
It was followed by a Richter 6.6 three and a half hours later. In theory, impossible. We were considerably relieved that the trio of events near Bukavu
(southern tip of Lake Kivu) in February 2008 was weaker and more easily understood: a Richter 5.9 on 2/3/2008 followed by a Richter 5.0 three and hours later (normal aftershock pattern) with a somewhat troubling 5.3 11 days later.