April 11, 2016
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion

Evaluation of Seismic Activities for March 2016

1 Major Seismic Activities

There was no remarkable activity.

• Seismic Activities for All of Japan in March 2016 (Magnitude 4.0 or over)

to supplementary reports

2 Nationwide Seismic Activities by Region

(1) Hokkaido Region

There was no remarkable activity.

• Hokkaido Region

to supplementary reports

(2) Tohoku Region

There was no remarkable activity.

• Tohoku Region

to supplementary reports

(3) Kanto-Chubu Region

* On March 22, there was a Magnitude (M) 4.7 earthquake at a depth of approximately 5 km in the northern Ibaraki prefecture. The focal mechanism showed a normal fault type with a tension axis in an NE-SW direction. This event occurred within the crust.

* In the GNSS data for the Tokai region, there has been no change of activity which is likely to be associated with the Tokai earthquake.

• Kanto - Chubu Region
• Earthquake in the Northern Ibaraki Prefecture on March 22
• Continuous GNSS Monitoring along the Line from Kakegawa to Omaezaki (Baseline Length and Relative Height)

to supplementary reports

(4) Kinki-Chugoku-Shikoku Region

There was no remarkable activity.

• Kinki-Chugoku-Shikoku Region

to supplementary reports

(5) Kyushu-Okinawa Region

* On March 3, there was a M4.9 earthquake at a depth of approximately 50 km under the southern plains of Miyazaki prefecture. The focal mechanism had a tension axis in an E-W direction. This event occurred within the Philippine Sea plate.

* On March 14, there was a M5.3 earthquake at a depth of approximately 220 km under the ocean area near Tokara Islands. The focal mechanism had a tension axis in the direction of the Philippine Sea plate. This event occurred within the Philippine Sea plate.

• Kyushu Region
• Earthquake under the Southern Plains of Miyazaki Prefecture on March 3
• Earthquake under the Ocean Area near Tokara Islands on March 14
• Okinawa Region

to supplementary reports

Supplement

* On April 1, there was a M6.5 earthquake offshore southeast of Mie prefecture. The focal mechanism of this event showed a reverse fault type with a compression axis in an NW-SE direction.

• Earthquake Offshore South-East of Mie Prefecture on April 1
• Earthquake Offshore South-East of Mie Prefecture on April 1: Distribution of Hypocenters
• Distribution of Hypocenters determined by DD Method
• The Different Positions of the Main shock and Aftershocks Checked by Observed Waveforms
• Low-Frequency Seismic (Micro-Tremors) Activity and Short-Term Slow-Slip in Nara and Wakayama Prefectures
• Earthquake Offshore South-East of Mie Prefecture on April 1, 2016: Super-Low-Frequency Seismic Activity in the Region Around the Hypocenter

Note: [ ] is the regional name of the epicenter used in the announcement of Japan Meteorological Agency.
     GNSS (Global Navigation Satellite System) is a general name of satellite positioning system such as GPS.

Supplementary Information to the Evaluation of Seismic Activities for March 2016

April 11, 2016
Earthquake Research Committee

1 Major Seismic Activities

The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during March, 2016.

• M4.0 or greater: 69 (67 events in February, 2016)
• M5.0 or greater: 4 (8 events in February, 2016)
• M6.0 or greater: 0 (2 events in February, 2016)

(reference)

• M4.0 or greater: 73 / month (Median number of earthquakes over the past 10 years from 1998 through 2007)
• M5.0 or greater: 9 / month (Median number of earthquakes over the past 35 years from 1973 through 2007)
• M6.0 or greater: 1.4 / month, approximately 17 / year (Average number of earthquakes over the past 84 years from 1924 through 2007)

The following events for the period from March 2015 to late February 2016 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activities."

to the text

2 Nationwide Seismic Activities by Region

(1) Hokkaido Region

There is no supplementary information for Hokkaido region.

to the text

(2) Tohoku Region

There is no supplementary information for Tohoku region.

to the text

(3) Kanto-Chubu Region

–"In the GNSS data for the Tokai region, there has been no change of activity which is likely to be associated with the Tokai earthquake.":
(This evaluation is in agreement with the views presented at the regular meeting on March 28 of the Assessment Committee for Areas under Intensified Measures against Earthquake Disaster (reference below).)

(Reference)

Recent seismic and crustal activity in the Tokai region and its vicinity (Seismological and Volcanological Department, Japan Meteorological Agency, March 28, 2016)
"No change of activity which is likely to be associated with the Tokai earthquake has been observed until now. (Excerpted)"

to the text

(4) Kinki-Chugoku-Shikoku Region

– Non-stationary crustal deformation surrounding the Kii Channel observed from mid-2014 is still continuing. This deformation is thought to be due to a slow slip (slow-slip) at the boundary between the Philippine Sea and the continental plates.

– From the GNSS observation, non-stationary crustal deformation surrounding the Bungo Channel was detected. This deformation is thought to be due to a slow slip (slow-slip) at the boundary between the Philippine Sea and the continental plates. This change began from around December 2015. Note that in this vicinity, long-term slow slips were observed in 1997, from 2003 to 2004, and from 2009 to 2010.

• Non-Stationary Crustal Deformation around the Kii Channel
• Non-Stationary Crustal Deformation around the Bungo Channel (1)
• Non-Stationary Crustal Deformation around the Bungo Channel (2)
• Distribution of Estimated Slip on the Plate Boundary Surface (1)
• Distribution of Estimated Slip on the Plate Boundary Surface (2)

to the text

(5) Kyushu-Okinawa Region

There is no supplementary information for Kyushu-Okinawa regions.

to the text