Finding Earthquake-Resistant Land in Japan: A Guide for Homebuyers

Understanding Ground Hardness and Earthquake Damage

The impact of an earthquake isn't solely determined by its magnitude. Two key factors influence damage severity:

• The earthquake's distance and depth

• The hardness of the ground underneath structures

Buildings on loose soil typically suffer more damage than those built on hard, solid ground. This difference explains why structures in the same area can experience vastly different outcomes during the same earthquake.

Japan's Ground Characteristics

Japanese urban areas often sit on relatively loose ground compared to cities in other countries. This is because many developed areas were originally:

• Rice paddies

• Rivers or river mouths

• Swamps or ponds

• Reclaimed land

You may be asking yourself why the Japanese would build cities in such unsuitable places. Japan is made up of mountains, where building is difficult or even impossible. As a result, people had no choice but to settle in the flat areas in the valleys or river basins. Tokyo is a good example of this. The Japanese capital was built around the marshy areas of the great Edo river. As is grew larger, the populace attempted to gain more room for expansion by filling in the mashes and the river mouth with rocks, dirt, and even rubbish. However, much of this land, particularly that which was reclaimed during the Edo period (1603-1867), is considerably less stable than naturally occurring solid ground.

How to Identify Stable Ground

1. Examine Old Maps

Historical maps reveal previous terrain features. Areas that experienced liquefaction during recent earthquakes often appear as bodies of water on old maps.

Resources:

• Geospatial Information Authority of Japan - Provides historical maps dating back to the Meiji period

• GSI Maps - Interactive map platform with historical overlays

• Liquefaction Risk Assessment Portal - Japan Seismic Hazard Information Station

2. Research Place Names

Japanese place names often indicate historical land features. Areas with names containing elements like "e," "kame," "sawa," "ura," "hama," or "shu" frequently indicate historical connections to water. These places will naturally be more susceptible to earthquake damage.

If the current name doesn't provide clues, check:

• Legal Affairs Bureau - For old land registers

• National Archives of Japan - Historical documents including some land records

Let's look at the example of Urayasu, a city in Chiba prefecture which is famous for being the location of Tokyo Disneyland. The kanji for Urayasu (浦安) combines two characters that reflect its historical geography:

• 浦 (ura) - This character means "bay," "inlet," or "coastal area." It contains the water radical (氵) on the left side, indicating its connection to water.

• 安 (yasu) - This character means "peaceful," "safe," or "tranquil."

During the 2011 Great East Japan Earthquake (also known as the Tohoku Earthquake), Urayasu City in Chiba Prefecture experienced particularly severe damage, especially from soil liquefaction, despite being approximately 380 kilometers from the earthquake's epicenter:

• Approximately 85% of the city's land area (primarily reclaimed land) experienced liquefaction

• More than 9,000 houses were damaged

• The city's infrastructure was severely affected with:

  • Tilted buildings and houses

  • Ruptured water and sewage pipes

  • Damaged roads with significant cracks and subsidence

  • Utility poles that tilted at dangerous angles

  • Sand boils (where liquefied sand erupted through cracks in the ground)

3. Consult Government Hazard Maps

For a quicker assessment, review government hazard maps which provide information about:

• Earthquake vulnerability

• Liquefaction risk

• Flooding potential

• Landslide danger

Resources:

• My Town Hazard Map - From the Ministry of Land, Infrastructure, Transport and Tourism

• J-SHIS - Japan Seismic Hazard Information System

• Tokyo Metropolitan Government Disaster Prevention Map - Example of a local hazard map

Mobile apps:

• Yahoo! Japan Disaster Alert - Includes hazard map information

• Safety tips - Official disaster information app for foreigners in Japan

Building on Unstable Ground

If you must build on less stable ground due to location requirements or inherited property, proper foundation work becomes essential:

1. Commission a professional soil investigation first

2. Implement appropriate ground improvement techniques based on the investigation results

3. Be prepared for additional costs associated with these measures

Professional resources:

• Japan Building Disaster Prevention Association - Information on construction standards

• Japan Geotechnical Society - Professional organization for soil engineers

Key Takeaways

• Loose ground significantly increases earthquake damage risk

• Japanese urban areas frequently feature less stable ground conditions

• Research using historical maps, place names, and hazard information

• When building on unstable ground, professional soil assessment and ground improvement are crucial investments