The percentage of bad earthquakes occurring in Japan has gone up.
この場合、次のような言い方ができますよ。
ーThe percentage of bad earthquakes occurring in Japan has gone up.
「日本で大きな地震が起こる確率が上がった」
The percentage of ... has gone up. で「…の確率が上がった」と言えます。
例:
It used to be that one in a hundred earthquakes would be a bad one, but now it's more like one in twenty.
「今まで100回に一回で大きな地震が起こるとされていたが、むしろ今は20回に一回に近い」
ご参考まで!