Tectonic stresses that cause rocks to break: earthquake activity = seismicity, seismicity occurs due to . Motion along a newly formed crustal fracture (or fault) Hypocenter = focus , spot within the earth where earthquake waves. Epicenter = land surface above the hypocenter: majority of quakes occur along faults. Common crustal fractures that move rock masses. The amount of movement = displacement: also called offset or slip, markers reveal the amount of offset, faults are like planar breaks in blocks of crust. On the sloping fault, crustal blocks are classified as: Faults & quakes originate: usually occurs on a fault surface, earthquake waves expand outward from hypocenter. Faults initiation footwall): footwall - block below the fault, hanging wall block above the fault, fault scarp difference in displaced ground elevation (small step, fault type based on relative block motion. Normal fault - hanging wall moves down relative to footwall: result from extension stretching.