What precursory phenomena (natural events) have been observed before some large earthquakes?

Predicting earthquakes is complex task and some precursors are given below.

Explanation:

1. Changes in animal behavior: Certain animals can respond to the P-waves that are being generated.

2. Emission of Radon gas: is most rocks contain this gas, as this gas can be isotopically distinguished. It's attributed to being release pre-seismic stress or shock waves.

3. Breaking of an ice sheet or landslides: These may be issued before some large earthquake.

4. Magnetic and electric charges like the density and thickness in the rock mass.

5. Shaking and vibration of water bodies.

xvx sorry didnt mean to answer this