Earthquakes and Tsunamis

1. Description

Earthquakes refer to the sudden shaking of the ground. As objects physically move during earthquakes, your surroundings can be damaged. Be careful inside rooms and buildings, as people can be injured by falling objects. Stronger earthquakes can change entire structures of buildings and natural landscapes, leading to destruction that can injure people.

Earthquakes that occur in the ocean have the potential to initiate tsunamis, which are massive waves generated by fluctuations on the ocean surface. Tsunamis that head toward coastal cities and towns can cause flooding, which in turn damages buildings, objects, and people.

2. Warnings and Advisory Information

Both earthquakes and tsunamis are caused by seismic activity, for which intensity describes the degree of shaking. The Japan Meteorological Agency ranks seismic intensity across ten levels ranging from 0 to 7 (please see the table below). Magnitude (M) is the energy of the earthquake. Even an earthquake with a small magnitude could have a large seismic intensity in areas near its source. Japanese TV outlets such as the NHK usually provide live reporting of all seismic activities measured 4 and above.

Seismic intensity：Human perception and reaction

0: Imperceptible to people, but recorded by seismometers.
1: Felt slightly by some people keeping quiet in buildings.
2: Felt by many people keeping quiet in buildings. Some people may be awoken.
3: Felt by most people in buildings. Felt by some people walking. Many people are awoken.
4: Most people are startled. Felt by most people walking. Most people are awoken.
5 Lower: Many people are frightened and feel the need to hold onto something stable.
5 Upper: Many people find it hard to move; walking is difficult without holding onto something stable.
6 Lower: It is difficult to remain standing.
6 Upper: It is impossible to remain standing or move without crawling. People may be thrown through the air.
7: It is impossible to remain standing or move without crawling. People may be thrown through the air.

Source: “Human perception and reaction, indoor situation, outdoor situation,” homepage of the Japan Meteorological Agency: https://www.jma.go.jp/jma/en/Activities/inttable.html

3. Tsunami Warning/Advisory

The Japan Meteorological Agency issues alerts about incoming tsunamis based on their size and geographical distribution. Ranging in magnitude, from relatively weak advisories to more urgent warnings and emergency warnings, these alerts are relayed by TV stations and over the web by media outlets such as the NHK. In the below table, we have summarized the content and definitions of different alerts.

Tsunami Warning/Advisory

Major Tsunami Warning**
Indication：Tsunami height is expected to be greater than 3 meters.
Expected damage and action to be taken：Wooden structures are expected to be completely destroyed and/or washed away; anybody exposed will be caught in tsunami currents.
Evacuate from coastal or river areas immediately to safer places such as high ground or a tsunami evacuation building.

Tsunami Warning
Indication：Tsunami height is expected to be up to 3 meters.
Expected damage and action to be taken：Tsunami waves will hit, causing damage to low-lying areas. Buildings will be flooded and anybody exposed will be caught in tsunami currents.Evacuate from coastal or river areas immediately to safer places such as high ground or a tsunami evacuation building.

Tsunami Advisory
Indication：Tsunami height is expected to be up to 1 meter.
Expected damage and action to be taken：Anybody exposed will be caught in strong tsunami currents in the sea. Fish farming facilities will be washed away and small vessels may capsize.Get out of the water and leave coastal areas immediately.

** Major Tsunami Warnings are issued in the classification of Emergency Warnings.
Detailed information on Emergency Warnings is provided on the Emergency Warning System web page.

Source: “Tsunami Warning/Advisory” homepage of the Japan Meteorological Agency:
http://www.data.jma.go.jp/svd/eqev/data/en/guide/tsunamiinfo.html#info1

4. Countermeasures

Proper countermeasures for earthquakes and tsunamis vary greatly depending on where you happen to be when disaster strikes. In the below paragraphs, we look at specific measures to take based on location.

If you are outside on the street, be sure to check whether billboards, window glass, and concrete blocks can fall over or drop from high places. Observe your immediate surroundings with calm and move to areas that seem to be the safest from the possibility of being hit with falling objects.

If you are in underground pedestrian zones, stand by large columns or walls. Follow instructions given by staff members in the area rather than rushing toward the nearest exit. Remain calm even during blackouts as emergency lighting will automatically switch on. If a fire breaks out in the immediate area, cover your mouth and nose with a handkerchief or a towel, lower your body, and move along the wall in the same direction as the smoke is flowing to escape.

If you are on the platform of a train station, you should move immediately to the nearest column to prevent falling into the train tracks or being hit with falling objects. If the platform is too crowded to allow for free movement, crouch down to the ground level and wait for the shaking to stop. Do not rush for the nearest exit or go in the train tracks. Stay on the platform and follow the instructions given by nearby staff members.

If you are inside a train, be mindful that the train can make a sudden emergency stop, causing people injury from hitting others or falling to the ground. If you are seated, you should put your bags over your head for protection. If you are standing, crouch down on the ground. For crowded trains where crouching is not possible, you should hold firmly onto handrails or straps to prevent falling over. Follow instructions given by crew members after the shaking stops.

If you are in a coastal area, immediately move to an area with higher ground. Continue to evacuate toward higher areas even after the initial tsunami passes, as tsunamis may repeatedly strike the same area multiple times within a short period of time. Do not return to coastal areas until it is publicly announced that it is safe to do so.

Source: “Actions when Earthquakes Occur,” e-College (Fire and Disaster Management Agency of the Ministry of Internal Affairs and Communications)
http://open.fdma.go.jp/e-college/study00/kiso/saigai_chishiki/jishin/06/index.html

Reference: page 30-31, “Disaster Preparedness Tokyo,” Tokyo Metropolitan Government

Source: Fire and Disaster Management Agency of the Ministry of Internal Affairs and Communications