The earthquake waves develop shadow zones because:
(i)The P and S waves follow a curved path in the interior of the earth which proves that the density increases inside the earth.
(ii)P and S waves are recorded along the surface near the focus of the earthquake. Beyond the depth of 2900 km ‘S’ wave disappear and P waves travel with reduced velocity
(iii)On reaching the core ‘S’ waves disappear and P waves are refracted as a result there is no wave for a distance. This area is known as shadow zone. Normally it is found between 105° to 145°.
