It will be better if you have defined whom you are referring when you are saying "they". But taking it on a broader view below points can be of help:
An earthquake may or may not be predicted in any of the following ways:
1. By way of the senses, in terms of witnessing changed animal behavior such as:
seeing burrowing animals out and about as though homeless at times that they usually are in their holes;
hearing and seeing birds in suddenly increased, agitated flight and communication patterns that just as suddenly stop;
feeling a pre-earthquake shock wave;
2. By use of scientific equipment such as:
creepmeters, to identify movement in the soil;
global positioning systems, to identify movement in the crustal [or lithospheric or tectonic] plates;
laser light, to identify movements that disrupt a light beam transmission over a fault line;
magnetometer, to identify magnetic field activity;
strainmeters, through the coordinated use of the seismograph and the seismometer, to identify vibrations.
seismograph are used to predict an earthquake
no
It is impossible to predict when an earthquake will occur.
It is impossible to predict when an earthquake will happen.
Hell yeah we can predict and earthquake
An oral or written account of previous earthquake activity and location in, near or on the meeting of tectonic or lithospheric plates may serve to predict the location of a future earthquake.
It is 'technically' impossible to predict when an earthquake is going to happen.
No.
methane
It is 'technically' impossible to predict if an earthquake is going to happen.
It is impossible to predict an earthquake of any magnitude.
You cannot forecast an earthquake, you can however predict the eruption of a volcanic eruption, an earthquake is unpredictable, as it is the result in a sudden release of pressure in the earths crust, if you could predict them there would be no deaths resulting from them.