was the highest in many places, but the third was reportedly higher in others. The ensuing waves came at intervals of 20 and 50 minutes. Flooding caused by the tsunami persisted in some areas for up to a month. Vestiges Due to urbanization and modernization in Niigata City and the surrounding area, in order to extract water-soluble natural gas in the ground water, water pumping quickly increased in 1950. As a result, land subsidence became a serious problem. Since 1959, due to restrictions on the extractions of natural gas and ground water in the Niigata city area, large scale land subsidence has lessened. However, in that period the ground was observed to settle an average of 20 cm a year. This land subsidence, the liquefaction in the inner city, and the tsunami all contributed to the massive inundation damage during the earthquake. The Bandai Bridge, one of the commuter bridges spanning the Shinano River in the city, survived the earthquake intact, but not unscathed. The streets that cross under the bridge on each side and run parallel to the river are approximately 1 meter different in elevation. The bridge itself only sank about 10 cm during the earthquake but coupled with the aforementioned land subsidence it has sunk a total of 1.2 meters. New laws concerning earthquake insurance were enacted in June 1966 in response to this earthquake. See also List of earthquakes in 1964 List of earthquakes in Japan 2004 Chūetsu earthquake References External links Niigata earthquake Niigata earthquake 1964 tsunamis June 1964 events in Asia Tsunamis in Japan Earthquakes of the Showa period