What do the bubbles on the USGS earthquake map represent?

[davenn]

Hi all

This morning, another large quake. This time a M 6.8 just offshore of SE New Ireland, PNG

M 6.8 - 20km ENE of Taron, Papua New Guinea

my seismogram

location map

cheers
Dave

 

[scottdave]

What do all of the "bubbles" represent on this map from the USGS site?

 

[davenn]

What do all of the "bubbles" represent on this map from the USGS site?

lots and lots of quakes over the last x number of years, size of the dot represents magnitude range ... It may say how many years ... let me go look

hmmm doesn't seem to specifically say in the main text, but since they are constantly referring to how many M x.x sized big quakes since 1900, it may well cover all quakes M5 and up since 1900

Ahhh, found the map key

M4.5 and up 1900 - 2015

Dave