Case2 /Analysis of Singularity Around Izu Region - the 12 Singular Epicenters (#SP12-1 to 12)

Interpretation of the 12 Singular Epicenters (#SP12-1 to 12)

Before explaining the screening method, we must define "Stages."

• 1st Stage: The first earthquake in a grid (0.1° Lon/Lat, 1 km depth).

• 2nd Stage: The first earthquake to exceed the magnitude of the 1st stage.

• 3rd Stage: The first earthquake to exceed the magnitude of the 2nd stage.

In the JMA database, 94% of M7.0+ earthquakes are 1st stage. Cases of 2nd or 3rd stages are extremely rare (only 12 cases total). We define these 12 cases of M7.0+ occurring as 2nd or 3rd stages as the "12 Singular Epicenters."

Among these 12, two groups of three consecutive earthquakes (Blue: #SP12-4 to 6; Yellow: #SP12-8 to 10) lie almost perfectly on straight lines with correlation coefficients of 1.0 and 0.9999.

• Blue Group: Located between Urakawa-oki and Offshore of Ibaraki Pref., moving nearly North-South on the landward side of the Japan Trench (1978–1982).

• Yellow Group: Follows an interesting line including the 1995 Kobe Earthquake, the 2016 Kumamoto Earthquake, and the 2016 Fukushima M7.4.

The remaining six epicenters (Orange) form a counter-clockwise loop enclosing a triangular region, similar to the Iki-Oki(壱岐・隠岐) case. This loop started with the 1930 North Izu Earthquake (near a plate triple junction) and traveled along the Nankai Trough, Izu-Ogasawara Trench, and Japan Trench, eventually reaching the 2024 Hyuga Nada M7.1.

E-Lng vs M chart / N-Lat vs M : They shows counter-clockwise direction moving similarly.

The similarity in the singularities shown here suggests that earthquake occurrence is not random, but follows specific rules or groups. The following analysis will further deepen this conviction.