THE JAPAN EARTHQUAKE & TSUNAMI AND WHAT THEY MEAN FOR THE U.S. Written by Michael Mahoney, March 17, 2011 Geophysicist, FEMA, National Earthquake Hazard Reduction Program (NEHRP) Coordinating Committee Member, FEMA, National Tsunami Hazard Mitigation Program (NTHMP) The Federal Emergency Management Agency (FEMA) and the multi-agency National Earthquake Hazards Reduction Program (NEHRP) joins with the rest of the United States and indeed the rest of the world in expressing our concern to the Japanese people as they recover from their historic magnitude 9.0 earthquake and resulting tsunami. Our thoughts and prayers go out to all who were affected by this ongoing tragedy. Immediately after the earthquake, NOAA’s Pacific Tsunami Warning Center and West Coast and Alaska Tsunami Warning Center both issued tsunami warnings for Hawaii, the U.S. West Coast, Alaska and the island territories in the Pacific. Fortunately, the tsunami generated by this earthquake which hit Hawaii and the West Coast caused relatively minor damage that was generally limited to beach front and harbor facilities. However, past tsunamis have been far worse, and the caution shown by Federal, State and local officials was certainly warranted. One only has to look back to 1960, when an earthquake in Chile resulted in a 35 ft tsunami in Hilo, Hawaii that killed 61 people to see that their caution was justified. WHAT HAPPENED IN JAPAN The Japan earthquake was on a subduction zone fault, where the Pacific tectonic plate is being pushed underneath Japan. This type of fault is responsible for the largest earthquakes and often generate large tsunamis. Interestingly, this earthquake was proceeded by a M7.2 and 3 M6+ foreshocks two days before. Fault modeling suggests a rupture zone of 350x150 km in size with peak slips of 18+ meters. Aftershocks from this earthquake have included one M7, almost 50 M6, and hundreds of M5 and smaller. In addition, this event also triggered separate earthquakes in western Honshu (M6.1) and offshore northwestern Honshu (M6.6). The earthquake damage in Japan was limited, partly because of the epicenter was almost 100 km from shore, but mostly due to the building codes that Japan has in force. Japanese building codes are more restrictive than those in the US as they call for building designs that are stronger and consequently more expensive. This philosophy appears to have paid off as we have not seen the collapse of any engineered buildings. While ground motion values may have been minimized by the distance of the epicenter, this was a very long duration earthquake, which is common for subduction zone events. Long duration shaking is something we may not have fully accounted for in our building codes and may have worked some building components to the point of failure where shorter shaking duration would not have. The only building collapses we have seen so far have generally been of older wood residential buildings. Japanese home construction traditionally uses heavy tile roofs for protection from typhoon winds. However, these heavy roofs can overtax a wood frame home if it is not properly built or maintained. While Japanese structures performed very well in the earthquake, we have heard many reports of damage to non-structural components, which are the building’s architectural elements, utilities,contents, etc. This type of damage continues to be a problem that we have documented in every earthquake, and is often responsible for greater dollar losses than actually structural damage. This type of damage often also results in the loss of function of the facility. A common example of this type of damage is damage to piping, such as fire sprinkler heads breaking from ceiling impact. This type of damage to a critical facility such as a hospital, this can greatly impact a community’s response and recovery. For residential buildings, this type of damage can include a water heater falling over if not strapped to a wall or the collapse of shelving or cabinets. The tsunami generated by this earthquake was measured as high as 33 feet (10 meters) and was responsible for most of the damage and fatalities that we are now seeing. It was the first tsunami to strike a modern, developed coastline, and it was devastating. While Japan generally incorporates seawalls and other structural protection to protect most developed areas, this tsunami overwhelmed all of these defenses. The tsunami reduced most of the wood frame homes to kindling. However, there were also some examples of larger, heavier multi-story concrete structures that survived the tsunami. The emergency management philosophy in both countries is that it is impossible to reasonably build residential structures that can withstand tsunami loads, and that the only way to protect the population is to train them to evacuate to high ground when a warning is given. For a tsunami whose source is far enough away, there are established warning systems that provide sufficient time for evacuations. For a near source tsunami like the one that just occurred in Japan, the warning is the earthquake itself. We have heard many reports of people evacuating to high ground, but obviously many were not able to evacuate. WHAT THIS MEANS FOR THE U.S. - EARTHQUAKE Our attention as both scientists and emergency managers can’t help but turn closer to home and wonder what effects a similar earthquake might have on our country. The National Earthquake Hazards Reduction Program (NEHRP) is responsible for the coordination and support of Federal earthquake-related activities; see www.nehrp.gov. FEMA, along with NIST, NSF and USGS, work to advance earthquake knowledge and awareness as well as reduce future losses. There are several lessons from the Japan earthquake and tsunami for the U.S. that the NEHRP agencies will try to capture. The earthquake confirmed the importance of proper building codes and building construction. The adoption and enforcement of an adequate building code is the most effective loss prevention measure that a State or community can do. This was the single most important difference between last year’s Haiti and Chile earthquakes, and it was proven again in Japan. Using funding under the NEHRP, FEMA has a long history of working the nation’s model building codes and consensus standards and continues to work with the industry to keep them current. However, building codes only work when the