In the last post, Dave asked if I had picked up a specific aftershock from the Great Honshu Earthquake. While I have picked up several aftershocks, even the larger ones may or may not be detected for a number of reasons. I have received notices for nearly eighty aftershocks of magnitude 5.5 or larger since the main shock. I also picked up a couple of the foreshocks occurring in the couple of days leading up to the magnitude 8.9 event. Some of the larger aftershocks immediately afterward were covered up by reverberations from the main event that lasted for at least four hours.
I have plotted the magnitude vs date/time for all of the notices I received during this earthquake sequence. The ones that I could see on my seismograph are annotated with the magnitude. I general, I can pick up magnitude 6.5 to 7.0 and greater earthquakes anywhere in the world but most often don’t because of poor alignment to my seismometer.