Hi Dennis. The 1995 Kobe earthquake in Japan (M=6.9) occurred along a previously unknown fault.
From my understanding there is no record going back 1000 years that indicates a quake of that magnitude has ever occurred there.

Japan sits on the intersection of four tectonic plates that generate a constant seismic risk. Kobe is relatively far from areas of collision and was considered (until recently!) to be less at risk than areas such as Tokyo.

Sediments in the area are predominantly formed from decomposed granite and from colluvial and alluvial deposits. Large areas of the city and its industrial areas were built on landfill sites in Osaka bay.

Ground movement associated with fault structures 1.7 m along the horizontal and 1.3 m along the vertical plane.

Massive Soil liquefaction of soft sediments occurred. Ground settlement was in the order of 0.5 - 0.75 m. lateral displacement 1-7 m. as a result many port facilities were destroyed or damaged. There were also numerous landslides and rockfalls.

Building Damage was mainly concentrated in a narrow band 1.2km wide and 30 km long. Largely associated with soft sediment. The majority of destroyed buildings in the area were unbraced. 1 - 2 story traditional houses. Wooden post and beams with Heavy roofs.

Damage also to steel and composite structures. But most damage confined to steel and concrete constructions built prior to 1980. Failures of these buildings largely associated with shear failure of columns.

Transportation facilities such as Railways and roads destroyed. The spectacular collapse of the Hanshin expressway was largely the result of its construction under older building codes. Gas and water disrupted for several months. Water to put out fires on day of disaster ran out after 2 hours.

Approximately 100 fires broke out within minutes of the earthquake. 1 million square meters of the city was burnt to the ground.

Lessons learned were the need to be clear about the subsurface soil characteristics.
Most of the buildings, which suffered severe damage, were built on soft sediment prone to liquefaction. Specially designed earthquake resistant building materials and designs did work well. Where these failed it was found to be the result of poor supervision of construction.

The chemical degradation of the concrete used in structures heightened the possibility of collapse. Some pillars in the Hanshin Expressway were only 425 of original strength due to the chemical degradation of the concrete. Take Care…Don in creepy town.

PS. Better half is Japanese. She is Americannized though. Now I'll catch if from the ladies.