TAIPEI (Reuters) -Earthquake warning smartphone apps have surged in popularity in Taiwan due to high demand from people eager to get a few extra seconds to take cover after more than 1,300 aftershocks rattled the island in the past month following a large temblor. Taiwan's east coast was struck by a 7.2 magnitude quake on April 3, killing 17 people. The frequent aftershocks since then - including more than 200 tremors in a 24-hour period starting April 22 - have unnerved many.