As Japan begins to rebuild after the massive 9.0 magnitude earthquake and tsunami, engineers are beginning to analyze the destruction to learn how to better prepare for future natural disasters; one expert says that prior to the earthquake, more infrastructures spending, particularly for projects aimed at preventing the approaching tsunami, could have mitigated much of the damage; the tsunami easily overwhelmed one of the tallest and longest seawalls in Japan; officials will have to decide whether to reinvest in costly tsunami infrastructure or to relocate communities further from the ocean to minimize the numbers affected by such events