On the whole, this has been a good thing for the area: the dramatic volcanic landscape attracts millions of tourists every year, as do the countless naturally-heated springs which bubble up all over the peninsula.
As it reaches the surface, the hot water is siphoned off and channelled into baths in the town's many ryokan, or traditional inns. The inn keepers of Izu owe their livelihoods to the rich volcanic waters, and some of the older ryokan contain small Shinto shrines dedicated to the subterranean gods (or devils) who make such prosperity possible.
But throughout this month, something thoroughly alarming has been going on underneath the Izu Peninsula. Yesterday, 150 people, including hotel owners, bar hostesses, and a Shinto priest, met on a beach in the town of Ito. They arranged a makeshift altar, and covered it with rice, sake, apples and strawberries. The priest bowed, clapped his hands and prayed - not in gratitude, but in supplication, for an end to a week-long seismic orgy.
The gods have gone berserk: between Monday last week and 11am yesterday, there were 8,758 earth tremors in the Izu peninsula.
Most of these were detectable only on a seismograph, but 427 have been strong enough to be felt by humans, even as far away as Tokyo. No one has been hurt and no serious damage has been caused: the strongest tremor has done no more than rattle the windows and topple ornaments off television sets. But the earthquakes are taking their toll - for two reasons they are turning out to be very bad news indeed for the peninsula and its people.
The first worry is what the tiny tremors may presage. Ever since the terrible Kobe earthquake, which killed more than 6,000 people in 1995, Japan has been on tenterhooks for the arrival of the next great Tokyo quake.
For several centuries, the city has been destroyed approximately every 70 years. The last one, which killed 140,000, came in 1923, which suggests that another one is due now. Earthquake prediction is a notoriously inexact science but, according to one theory, intense seismic activity in Izu could be an immediate preamble to the Big One.
And whatever pain the gods might have in store for Tokyo, towns like Ito are hurting now. Of its 74,000 inhabitants, seven out of ten are involved with the tourist industry.
Apart from the inconvenience of being shaken awake several times a night, the town's economy is being seriously rattled. By yesterday, some 80,000 people were reckoned to have cancelled their reservations. Thetremors have cost Ito as much as two billion yen (pounds 10m).
Things quietened down on Sunday but yesterday morning, the rattling started again. "We have to learn to live with earthquakes," said Tadashi Makino, director of the Ito City Tourist Association. "It is thanks to the volcanoes that we have the hot springs. It would be great if the mayor could announce that it's all safe, and we could start a PR campaign. But the quakes haven't stopped, and there is nothing we can do."