1 Inflammation of the gingiva, bone loss, and increased gingival recession may progress slower than with other forms of periodontitis.  Periodontitis Associated with Systemic Diseases - Systemic diseases, such as heart disease, diabetes, and certain forms of arthritis, may have a correlation with periodontitis.
Along Faults. Earthquakes can also occur far from the edges of plates, along faults. Faults are cracks in the earth where sections of a plate (or two plates) are moving in different directions. Faults are caused by all that bumping and sliding the plates do. They are more common near the edges of the plates.
The common points where the plates touch one another is where the earthquake starts or the focus. As seen in the picture above, subduction zones are on the borders of each tectonic plate. As they crash together one plate moves below the other which causes subduction zone earthquakes. Earthquakes are one of the biggest natural disasters known to man. Earthquakes occur when there is a sudden release of energy below the earths crust at the focus.