KYOTO - Although I am a foreigner, I am no stranger to Japan having visited many times and am now in the middle of my second one-year academic appointment at the Disaster Prevention Research Institute of Kyoto University. The June 18 earthquake that struck northern Osaka Prefecture was not the first earthquake I have experienced in Japan.
My first visit to Japan was in January 1995 to participate in the 4th U.S.-Japan Workshop on Urban Earthquake Hazard Reduction. I arrived in Osaka on Jan. 16, the day before the workshop was to begin. The workshop was scheduled to open on Jan. 17, but at 5:46 a.m. I was awakened by severe shaking generated by the Great Hanshin-Awaji Earthquake. Needless to say, our workshop turned into earthquake reconnaissance and my intended four-day stay was extended to three weeks. I returned multiple times over the next two years as I completed a study of the emergency response to that earthquake.
We learn a great deal from major earthquakes. The Hanshin-Awaji earthquake demonstrated the vulnerability of many elements of urban infrastructure — elevated freeways and bridges, many types of buildings as well as single family homes, harbor facilities and utilities. In addition, earthquake emergency response plans proved inadequate and existing seismic networks were in need of expansion to provide more rapid and accurate data on future earthquakes and their aftershocks. In response, new stronger building codes were developed and enforced, emergency operations plans were improved and the seismic network was significantly expanded.
So, what has been learned from the recent Osaka earthquake? There were five fatalities, two were victims of collapsed masonry walls and two died in their homes when heavy unsecured furniture fell and crushed them.
The building code was changed in 1978 after fatalities occurred during an earthquake in Miyagi Prefecture also from the collapse of masonry walls. Regrettably, these code changes applied only to new construction, leaving tens of thousands of older masonry walls in place all over Japan.
On June 18, 9-year-old Rina Miyake and 80-year old Minoru Yasui became the victims of masonry wall collapses, a known hazard. The three other fatalities were the victims of household hazards that have also been known for a long time: tall, heavy, unsecured bookcases that fell, causing fatal injuries.
During the four hours of television news coverage following the earthquake, a Meteorological Agency spokesman announced that people in the Osaka/Kyoto region should expect additional earthquakes in the form of aftershocks of the magnitude 6.1 earthquake. He also mentioned that there was a chance that another strong earthquake could occur over the next several days. This informal “advisory” was very important because scientifically, we know that some earthquakes are, in a small percentage of cases, precursors to additional large potentially damaging earthquakes.
Examples include the Great East Japan Earthquake and tsunami that was preceded on March 9 by three magnitude 6 earthquakes and a magnitude 7.4 event. Two days prior to the magnitude 7.3 Kumamoto earthquake of April 16, 2016, there was a magnitude 6.5 foreshock in April 14. While most earthquakes occur without foreshocks, there are a small number of cases where the first significant earthquake is not the last.
So, the Osaka earthquake reminded us that there are still household hazards that require mitigation as well as structures in our communities that pose life safety hazards. Both are serious but the older masonry walls that are so common in Japan require special attention.
Since the wall collapse that killed the elementary school student was located on school property, there have been calls for school districts throughout Japan to have similar walls on school property evaluated by structural engineers and either reinforced or replaced. This is a good beginning, but school districts and their properties are not the only ones that pose hazards for children walking to and from school and there should be national legislation that requires walls to be structurally sound for the safety of everyone.
One week after the Osaka earthquake, The Japan Times reported 417 injuries and 8,089 residences damaged. Since the earthquake did not cause any residential buildings to totally collapse, most of the injuries and three deaths were caused by household and, to some extent, workplace hazards including the movement of heavy furniture or falling objects, physical movement by occupants during the shaking, or injuries acquired during cleanup following the earthquake.
These injuries could be greatly reduced by measures that most people could take by themselves at home — bracing tall bookcases, locating heavy objects on lower shelves, securing appliances and installing cupboard latches that would prevent glassware and dishes from falling and breaking. Having shoes by the bed would reduce cuts from broken glass. There are excellent checklists of these measures available from the Meteorological Agency and local government disaster management agencies.
Finally, the Meteorological Agency should be commended for reminding residents of the Osaka and Kyoto region that the June 18 earthquake may not be the last strong earthquake they would experience.
Seismologists cannot predict earthquakes with accuracy but studies and our own experience in recent earthquakes has demonstrated that a single significant earthquake and its aftershocks are not the only pattern in which earthquakes occur. Sometimes an earthquake, even a fairly large one, is only a prelude to something stronger.
There are efforts currently underway to develop plans for issuing earthquake advisories for earthquakes or other potential seismic precursors that, upon evaluation by scientists, may increase the chances of large earthquakes over a period of a few days. These advisories must be accompanied by recommended actions by the public, private sector entities and government agencies. These advisories could lead to actions that reduce earthquake hazards, and the loss of life, injuries and damage. These are the lessons of the Osaka earthquake. Communities and individuals should act on them.
James D. Goltz is a visiting research professor at the disaster Prevention Research Institute of Kyoto University.