A list of things to consider when assessing tree health and possible tree failure:
Did you see any recent changes in the tree?
Is the tree tilting?
Is the earth on one side of the tree rising?
Is there cracking in the soil next to the trunk?
Are there dead branches, or early leaf drop?
Are there insects or insect holes?
Are there horizontal cracks in the trunk?
Is the canopy thinning?
Are there mushrooms near the trunk?
Was there construction or landscaping near the tree recently?
Has there been utility work or sewer line construction?
Answering yes to any of these questions could suggest problems, so it’s best to seek out expert advice.