प्राथमिक भूकम्पीय तरंगों (P-तरंगों) को उनके कणों के संचलन के आधार पर अन्य किस नाम से जाना जाता है?

According to Reid's Elastic Rebound Theory, earthquakes occur when:

The point within the Earth where an earthquake originates is called the:

Which device is used to detect and record an earthquake?