Location is Pacific Northwest (15 mi W of Portland, OR)
A 2-inch diameter branch broke off my backyard maple tree at the trunk this afternoon. The branch had many healthy-looking leaves and seed "helicopters" on it. The leaves show no obvious signs of disease or insect damage.
However, most of the wood was extremely brittle, as if it was dead or almost dead. The only parts with any flexibility were near the distal ends. Branches closer to the trunk end snap like dry kindling, and this is why the main branch broke off.
To my untrained eye there doesn't seem to be evidence of rot or disease, the wood is just very brittle and fragile.
Is the tree in trouble? The main trunk is about 24" in diameter but splits into two trunks about 8 feet above ground. I don't know how old it is.
Here are some pictures
Closeup of trunk branching:
Where the branch broke off, from the right side. In the first image this is hard to see, it's about 5/6 of the way up on the right-hand trunk and points straight at the camera, so it blends in with the trunk behind it.
Closeup of the broken branch trunk end
Another shot of the break, from the other side.
As requested, a cross-section through the broken branch.