Yesterday’s (28 Nov) large (but thankfully deep) quake in Peru was accompanied by a series of other quakes all down the west coast subduction zone. This was after a good many days with almost no activity (M>4) in this area. Today (29 Nov), no more quakes, instead a cluster of quakes in the far west of Indonesia and a string of smaller quakes east along the Aus - Indonesia boundary? I am not saying the two days are linked, I am saying that the daily activity is! It seems that the effect is limited to other parts of the same plate boundary, suggesting stress transfer directly through connected rocksrather than remote triggering through familiar sub-surface seismic waves? I am not sure how to test my idea further, associations all qualitative so far, but more than just a guess (but only just!)?
Busy day today (42 quakes >M4) and I reckon they are definitely ‘clustered’ too. One group down the Andes again (strange after a gap day before), one cluster in Central America, again a reactivation of a previous cluster / swarm from earlier in the year - a gap of months rather than days though? Clustered activity in S Japan and Indonesia too, the rest of the registered quakes seem pretty randomly scattered - as they usually are anyway on ‘low number’ days. So clustering suggests a link between the individual quakes on the same day, but also results in increased number of large quakes on a single day, a situation that can then either disappear within a day, or extend to several days or longer for a major swarm (although swarms are generally associated with mainly M<4 quakes from my previous qualitative review / memory). Am I making any kind of sense, or just rambling?