(Reference 3)

Notification No. 4 of the Japan Meteorological Agency

The seismic intensity scale used for observation of seismic intensity on Table 2-A-(6) of Article 1-2 of the Meteorological Operation Act. Regulations (Ordinance No. 101 of the Ministry of Transport, 1952) were stipulated as follows. Please note.

February 15, 1996 Kozo Ninomiya, Director-General, the Meteorological Agency

JMA seismic intensity scale

Scale Instrumental seismic intensity Scale Instrumental seismic intensity
0 Below 0.5 5Lower 4.5 or above and below 5.0
1 0.5 or above and below 1.5 5Upper 5.0 or above and below 5.5
2 1.5 or above and below 2.5 6Lower 5.5 or above and below 6.0
3 2.5 or above and below 3.5 6Upper 6.0 or above and below 6.5
4 3.5 or above and below 4.5 7 6.5 or above


Instrumental seismic intensity* means the value calculated from the following formula, as an index of seismic ground motion.
I = 2 log (a0) + 0.94
I is the instrumental seismic intensity.
a0 is the maximum value of a that satisfies Integral(w(t,a)dt)>=0.3
In this case, the integration range is in the duration of continuation of seismic ground motion.
t = time (unit is seconds).
a is the parameter related to the rate of acceleration of seismic ground motion.
(unit is centimeters per square second).
w(t,a) is the function: w(t,a) = 0 when v(t)<a,
and w(t,a) = 1 when v(t)>=a
v(t) is the vector-composed value (the unit is centimeters per square second) of the acceleration of three orthogonal components of seismic ground motion at t (values obtained by respectively multiplying the Fourier-transformed values for each component by the values calculated according to the formula in the right-hand column of the attached table, according to the type of filter presented in the left-hand column of the same table, and then by reverse Fourier-transforming them).

Attached Table

Type of filter and formula

Type of filter


Filter that represents the effect of period


High-cut filter

(1 + 0.694y2 + 0.241y4 + 0.0557y6 + 0.009664y8 + 0.00134y10 + 0.000155y12)-1/2

Low-cut filter

(1 - exp (- f/0.5)3)1/2


f is the frequency of seismic ground motion (unit is Hertz).
y is the value obtained by multiplying f by 1/10.

Additional rules

(Enforcement period)

1. The above notification will be enforced from the day of promulgation, and shall be applied to earthquake observation that will be conducted on April 1, 1996 (in the next clause, referred to as "application date") and thereafter.
(Special case of application of the JMA seismic intensity scale)

2. As to the special case of application of the JMA seismic intensity scale, there will be changes as follows in the table from the application date until September 30, 1996.


5 Lower

4.5 or above and below 5.0

5 Upper

5.0 or above and below 5.5

6 Lower

5.5 or above and below 6.0

6 Upper

6.0 or above and below 6.5



4.5 or above and below 5.5


5.5 or above and below 6.5