When an earthquake strikes, fires start simultaneously in many places. The combination of dispersed firefighters’ ability to extinguish fires, broken buildings and unusable roads, broken water supplies and water shortages, and congested roads with many cars makes it very difficult to extinguish fires. For these reasons, large-town fires are more likely to occur during earthquakes. This is especially true in wet areas like Japan, where buildings are mainly made of wood and fires can spread over them as they break down, causing more damage. In dry areas, many houses are made of brick or stone, which are often completely destroyed by earthquakes.

During the Great Kanto Earthquake of 1923, 320,000 houses, or about 62% of the houses in Tokyo, were burned down. There were 136 fires, 76 of which spread widely, burning as much as 44% of the city in three days. Almost all (95%) of the deaths were caused by fire. Almost the same proportion (63%) of houses burned down in Yokohama. History shows that every time there has been a major earthquake, there has also been a major fire. The basic measure against fires caused by earthquakes is to make the house earthquake-proof and prevent it from collapsing.

source:
https://dil.bosai.go.jp/workshop/2006workshop/gakusyukai11.html