Gear reduction on large turbofans
Those with gear reduction are called geared turbofans (GTFs). In general, you can check the Wikipedia article on any engine, see its classification and specifications, and also check the linked citations.

The GE90 and Trent 1000 are not geared turbofans. Wikipedia lists only 5 geared turbofans, with the biggest (a recent engine; first run 2008; entry into service 2016) powering the A320neo family (narrow-body jetliner) and other regional jets.

Because of the immense torque of large turbofans (thrust >200 kN), it is not yet feasible. It took 20 years to develop the ~100 kN PW1000G.$^1$ It took that long to ensure the new components are maintenance free (apart from oil changes). So for the time being GTFs are outliers, and when a turbofan is one, it would be stated.

Prior to the PW1000G, there is the ALF 502/LF 507 from the 80s that still powers the 146/RJ. The ~30 kN GTF was designed/chosen for its relative quietness for operating from noise-sensitive airports.

Note: the fan blades are not welded, rather connected/attached. You can watch a fan removal here (noisy video).



$^1$ http://large.stanford.edu/courses/2014/ph240/suresh1/docs/pwspecs.pdf