Development of Warning System for Earthquakes

A solution to safety from earth’s natural disasters? A 10-second warning may not sound like much, but when it comes to natural disasters, early warning systems seem to be the answer.

In the photo, an early-warning text message reads: “An earthquake at Fukushima-oki has begun. Please be prepared for strong tremors.”

The devastation of Japan’s Tōhoku earthquake of 2011 still resonates for many. On March 11, 2011, a magnitude-9 earthquake shook north-eastern Japan, unleashing a savage tsunami. The number of confirmed deaths was 15,894 as of June 10, 2016, with more than 2,500 people still reported as missing.

An earthquake is a discernible tremor in the surface of the Earth, which is initiated by seismic waves occurring from the sudden release of energy in the Earth’s crust. It originates from the movements of tectonic plates below the surface of the earth. These motions produce seismic waves which transmit through the earth. A tsunami is a powerful series of waves that result from a sudden disturbance of the ocean floor due to earthquakes, underwater landslides, volcanic eruptions, meteorites or asteroids. The primary factor that influences tsunami generation is earthquakes.  An earthquake on the ocean floor can result in a sudden rise or fall of the earth’s crust. This movement can cause water above to rise or fall, creating tsunami waves.

Earthquake history in Japan

Japan has an infamous earthquake history as the country is prone to experience 2-3 earthquakes daily, resulting in 1,500 earthquakes per annum. Contrastingly, the rate of tsunamis is one occurrence every ten years. In the previous five years, from 2014 to 2019, Japan has experienced seven major earthquakes and one tsunami which have struck the island nation.

Japan has an advanced and well-preserved infrastructure, which consistently undertakes upgrading and expansion. The Tōhoku earthquake caused unthinkable devastation, contributing to more than 125,000 severely damaged buildings, an estimated worth of more than $310 billion. Earth tremors are the primary cause of an earthquake’s immense damage to man-made structures.

Buildings and infrastructure are not sufficiently resistant for the intense levels of shaking that can occur from an earthquake. As a result, the collapse of structures plays a principal role in the death toll. In addition, great fatalities and property damage in coastal regions are sourced from tsunamis. Buildings and objects are damaged by the weight of the water, generally reduced to skeletal foundations and exposed rock.

The Importance of Forewarning

Earthquakes and tsunamis claim thousands of lives worldwide. Forewarning authorises people to seek safety which in a matter of seconds could be the difference between life and death. Japan has the most advanced earthquake early-warning system in the world. The nationwide system launched in 2007, observes tremors and calculates an earthquake’s epicentre. This system provides an advance announcement of the evaluated seismic intensities and predicted arrival time an earthquake.

When a substantial seismic activity happens, changes in the sea level are observed by surface buoy sensors. Tsunami warning centres monitor the data, perform analysis, and determine whether conditions are met to issue alerts to government officials and the mass media, such as radio, television, and communication companies.

The warnings can appear seconds to minutes before a natural disaster which permits at-risk individuals, communities and organisations to prepare and act appropriately and within sufficient time to minimise harm. The alerts are aimed to reduce the impact of natural disasters from many sectors of society with countermeasures which will reduce injuries, fatalities, the economic and material impacts. With the provision of lead time, individuals are inclined to take protective measures by escaping to higher ground, seeking protection from falling debris or evacuating from hazardous environments before they are overtaken by these events.

Conclusion

The duration of time from the announcement of an Earthquake Early Warning until the arrival of the main tremors is within a matter of seconds. Areas that are adjacent to the centre of the earthquake are affected as the warning may not be transmitted before strong tremors strike. Using data from only one seismograph can generate false Earthquake Early Warnings from factors of noise from accidents, lightning or device failure. Consequently, too many false alarms in both an earthquake and tsunami warning system would weaken faith in the systems and inaccurate or inappropriate information could deceive or delay evacuation and increase the loss of lives.

Furthermore, it is difficult to separate earthquakes and provide accurate warnings when multiple occur simultaneously or near one another. During the 11 March quake, many of the sensors were taken offline by the tremors and tsunami waves. In addition, because of the large magnitude of the earthquake, the remaining sensors were overloaded with data making the results difficult to interpret. Additionally, the underestimation of the tsunami’s height likely contributed to the delay in people’s evacuation, restricting their escape from waves at heights up to 120 feet.

References

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• JMA 2019, Limitations of the earthquake early warning, JMA, viewed 11 August 2019.