Without knowing a specific area to look at it's hard to say what the issue might be but I will say I'd strongly recommend against using the JPG for your displacement data source. Not only is it an 8 bit per channel format, meaning you'll only have a max of 256 possible levels of height, it also uses "lossy" compression. You can see how bad this can be if you adjust gamma and contrast in your source JPG file to exaggerate the JPG artifacts, you can see a lot of noise in what is supposed to be flat areas of sea. Even though this noise is probably very close to the same grayscale value as the surrounding area, because you're working with such a limited range of height values, it actually can be significantly different in height, certainly destroying any sense of a (nearly) flat ocean. For example, if the noise (from compression) is just 1 grayscale value away from absolute black, it will be 1/256th of your total displaced height range above it. Since you're displacing 11,000 meters, that's a 43 meter difference, about 150 feet, and that is quite a big wave!
So, ideally you'd find a better source of displacement data. That doesn't necessarily mean it's the source of your problem, but it surely isn't helping you to get an accurate Earth.
- Oshyan
