Petra, I don't really have anything to add to John's comments. I noticed the lack of aftershocks also, and assumed that there had to be aftershock for a M4.4 or 4.6; they just are not making it onto the map....A question would be whether or not UCSB people went out and put in some temporary local stations along the shore. There are oil fields near the location of the quake....or a little seaward of the quake....there may be a seismometer on one or more of the 3 platforms. As I have posted here before, the platforms have more to worry about than the shaking in a quake....there is a very large submarine landslide in this area, and many have suggested that it was triggered by the M7++ 1812 earthquake. The slide would then have been responsible for the local tsunami....
Chris