The Methods Used to Make Estimates of the Probability of 2 Hazard Events Occurring.

Around the world, there are at least 50 earthquakes every year. 
There are many ways that can be utilized in diagnosing an active volcano. Such methods include the visual warning signs. For example, if there is smoke or steam rising from the mouth of the volcano and in areas close to the volcano. This is mostly from the sulfur being released from the earth. Another way this can be diagnosed is through the use of an equipment called a correlation spectrometer. A correlation spectrometer is a device that can measure the amount and density of volcanic gases. 
The methods of diagnosing an active volcano is not limited to just the correlation spectrometer, there is another device that is popularly used. It is called a Seismometer. A Seismometer's basic function is to record minor and major earthquakes at least 4 miles below surface in the form of Seismic waves.
 Other methods include ground deformation reading, and thermal monitoring.
 Ground formation is monitored because ground swelling will indicate whether or not there is an increase of sulfur dioxide below the surface. Movement of magma and changes in gas releases thermal activity which can be seen through the use of infrared radiometry.