The Aug. 7, 2000 Alliance Ohio EQ
This earthquake occurred in northeastern Ohio, yet not too close to Ashtabula. Thus it provides a valuable test of whether the "LLg" phase is only generated and propagated along the Lake Erie coast. This event was well-recorded across the region.
Lets look at some seismograms of the Alliance EQ, here is COWO at a distance of about 75 km.
We can see the large amplitude LLg wave above, hence the LLg phase is not exclusive to the Lake Erie shore.
OSLO is about two hundred km epicentral distance.
We see that LLg is now a well-dispersed wavetrain with amplitude similar to the S wave.
SSUO is at about three hundred km epicentral distance.
LLg is still present at seismogram right edge as a well-dispersed wavetrain with amplitude still similar to the S wave. Note that the "official Lg" is now beginning to emerge just 5 to 10 seconds behind the S wave.
Even further, UOCO is about 360 km epicentral distance.
LLg is still present at the seismogram's right edge as a well-dispersed wavetrain with amplitude still similar to the S wave. Hence, LLg amplitude is as easy/difficult to measure as S or Lg at these far distances.