This is the 3148th most frequent Japanese word.
割れ
"割れ" means "crack" or "split" in English.
Here, '割れ' is a conjugation of the verb '割れる' (to break) in its past form, used to describe the state of the glass having broken.
ガラスが割れてしまった。
The glass broke.
In this sentence, '割れ' appears as a noun derived from the verb '割れる' and it implies a split or crack metaphorically associated with trust.
彼の言葉には、信頼の割れ目が見える。
In his words, a crack in trust can be seen.
Here, '割れ' is a noun indicating a physical crack or split resulting from an earthquake.