Earthquake Research in China  2019, Vol. 33 Issue (3): 525-534     DOI: 10.19743/j.cnki.0891-4176.201903013
Summary of Global Earthquake Disasters in 2018
FENG Wei1, ZHU Lin2, QIAN Geng3
1. Institute of Earthquake Forecasting, China Earthquake Administration, Beijing 100036, China;
2. Development Research Center of China Earthquake Administration, Beijing 100045, China;
3. Key Laboratory of Earthquake Geodesy, Institute of Seismology, CEA, Wuhan 430071, China
Abstract: According to global seismic hazards data in 2018, the paper summarizes major hazards data of the global earthquakes, describes the major seismic hazards, and analyzes the characteristics of disasters losses of hazard earthquakes in this year. Focusing on the disaster and the cause of the September 28, 2018, Indonesia earthquake, and listing the major earthquakes triggered the tsunami disasters in history. Finally, giving suggestions and measures to deal with the earthquake disasters effectively.
Key words: 2018     Earthquake disaster     Global

INTRODUCTION

Earthquakes are the natural disasters that cause the most deaths. In order to better understand the global earthquakes, according to the USGS/CEIC and CENC earthquake catalog data, the Associated Press, Agence France-Presse, Destructive Physical Analysis, Kyodo News and other foreign companies, the real-time data on earthquake disasters in the"Central News Agency"and Xinhuanet departments, this paper statistics the global earthquake disasters information of 2018. At the same time, a detailed description of the more serious earthquake cases is given, and the main factors causing casualties are analyzed. In addition, the major quake-triggered tsunamis in Indonesia from 1990 to now are counted, and the disasters caused by them are described.

1 GLOBAL SEISMICITY IN 2018

According to the seismic observation data of CENC and USGS/NEIC, 118 earthquakes with M≥6.0, 16 earthquakes with M≥7.0 and 2 earthquakes with M≥8.0 occurred in the world from January 1, 2018 to December 31, 2018. In the second half of the 20th century, the annual average level of global earthquakes was 165 (±5) earthquakes with M≥ 6.0, 17 (±2) earthquakes with M≥7.0, 0.7-0.9 earthquakes with M≥8.0(Dunbar P.K. et al., 1992; Feng Wei et al., 2013, 2016), so the global seismicity level was low in 2018.

According to the energy calculation formula proposed by Gutenberg (Department of Earthquake Monitoring and Prediction, CEA, 2007):

 ${\rm{lg}}E(E{\rm{rg}}) = 1.5M + 11.8$ (1)

It is estimated that the total energy of seismic wave released in 2018 is about 3.0×1017J, which is the average value of 2.9×1017-4.2×1017J during the 20th century.

2 SUMMARY OF EARTHQUAKE DISASTER

According to statistics, there are 33 earthquakes that cause casualties around the world in 2018 (Fig. 1). The total number of deaths in the earthquake was about 3, 200 and the number of injures was about 21, 900. Compared with previous years, the number of earthquake deaths in 2018 is lower than the average number of deaths in the past 110 years (the average annual death toll in the 1900-2014 earthquakes is about 21, 700), it is also much lower than the average in the last 20 years (the average annual death toll in the 1995-2014 earthquakes is about 50, 050). The earthquakes causing more casualties were the Hualien M6.4 earthquake in Taiwan, China on February 6, with 17 deaths and 277 injuries; the M6.7 earthquake in Papua New Guinea on March 6, with 25 deaths and hundreds of injured; the M6.9 earthquake in Indonesia on August 5, with 563 deaths and thousands of injured; and the Hokkaido M6.6 earthquake in Japan on September 5, with 42 deaths and 680 injuries; 2, 256 deaths, 10, 679 injuries and hundreds of missing in the M7.5 earthquake in Indonesia on September 28; 18 deaths and 548 injuries in the M5.9 earthquake in Haiti on October 7.

 Fig. 1 Distribution of the hazard earthquakes in 2018
3 SUMMARY OF IMPORTANT DISASTERS AND EARTHQUAKES IN 2018 3.1 Earthquake in Papua New Guinea

On February 25, 2018, M7.5 earthquake occurred in Papua New Guinea. The earthquake triggered secondary disasters such as debris flows and landslides. Many schools, residential buildings and other buildings were severely damaged, and local oil and gas operations were forced to stop. More than 10 aftershocks with M≥5.0 occurred after the strong earthquake, but no tsunami warning was issued. Landslides destroyed roads in some areas and many schools were suspended.

Table 1 List of the world's major earthquake disaster in 2018

Papua New Guinea is a South Pacific island country belonging to the Melanesian Islands and consisting of more than 600 large and small islands throughout the country. Papua New Guinea is located at the intersection of the Pacific Plate and the Indian Ocean Plate, with frequent earthquake volcanoes. In the past five years, more than 50 earthquakes of magnitude 6 and above have occurred in Papua New Guinea and its adjacent waters. The largest earthquake was the magnitude 7.8 earthquake that occurred in New Ireland on December 17, 2016.

The earthquake caused 160 deaths, more than 500 injuries, 143, 000 people were affected, and about 20, 000 people were homeless. The earthquake triggered landslides and mudslides, and caused widespread blackouts. Many buildings were seriously damaged, which was the most casualties in Papua New Guinea in 2018.

3.2 Earthquake in Lombok, Indonesia

On August 5, 2018, an earthquake of magnitude 6.9 occurred in Lombok, Indonesia. The earthquake caused a number of secondary disasters such as landslides and mudslides, causing 563 deaths and more than 7, 000 injuries. The earthquake also caused serious problems in some schools, residential buildings and other buildings. Lombok and Bali airports were damaged, some roads were seriously damaged, and direct economic losses amounted to 5.04 trillion rupiah, equivalent to about 2.4 billion yuan.

The earthquake caused more than 500 aftershocks, damaged more than 80, 000 houses and public buildings, forced the evacuation of more than 270, 000 local residents, and caused many landslides on the island's Linjani volcano. After repeated strong earthquakes in Longmu Island, not only serious casualties have been caused, but also landforms have changed. The whole island decreased by 5-15cm, and the northern part of Longmu Island is 25cm near the epicenter of the earthquake.

3.3 Earthquake in Hokkaido, Japan

The epicenter of the earthquake was on land and did not trigger a tsunami, but the earthquake caused mountain collapses, including more than 10 houses collapsed and more than 20 people were buried in Atsuma-Cho. The earthquake caused 42 deaths and more than 680 injuries. Hokkaido, Aomori-Ken, Iwate and Miyagi counties were strongly affected by the earthquake. Many buildings collapsed seriously in the epicenter area. The earthquake also caused a large-scale power outage and water cut-off in the whole Hokkaido area. About 2.95 million households were affected. Several serious landslides occurred in Houshending near the epicenter, which was the most serious disaster area.

3.4 Earthquake on Sulawesi Island, Indonesia

On September 28, 2018, an M7.5 earthquake occurred in the Sulawesi Island, Indonesia. The earthquake was a shallow strike-slip earthquake with positive rupture in some areas. The co-seismic deformation field occurs at the boundary of the Indian Ocean-Australia plate, Eurasian plate and Philippine plate. There are many micro-plates in the region, and the structure is very complex. According to the co-seismic deformation field, it can be preliminarily determined that the Palu Koro fault ruptured during the earthquake. The interferometric displacement shows that the influence range of deformation field is about 200×50km. The maximum positive and negative deformations of the satellite line of sight are 0.7m and -0.7m respectively. If the LOS deformation is completely caused by the strike-slip motion, the deformation variable parallel to the fault is about 5m by consideration of the strike of the fault at the maximum point; if the LOS deformation is completely caused by the vertical deformation, the LOS direction of 0.7m Deformation means a vertical deformation of 0.8m.

The earthquake triggered a tsunami in the coastal area of Palu. At least two cities were attacked by the tsunami, a large number of buildings were washed away, tens of thousands of houses were damaged, the earthquake caused many aftershocks, and caused a large-scale blackout. The earthquake caused 2, 256 deaths, 10, 679 injuries, the earthquake caused many buildings such as hotels, schools collapsed or by waves. It also causes secondary disasters such as land liquefaction, landslide and debris flow.

Indonesia is a country with frequent earthquakes and volcanoes in the world. Several strong earthquakes have occurred in Indonesia since 2018. Strong earthquakes occurred successively in Longmu Island and adjacent sea areas in Indonesia from July to August, causing huge casualties and economic losses. In terms of location, Indonesia is located at the junction of the Pacific Plate, the Indian Ocean Plate and the Eurasian Plate, and also at the junction of the circum-Pacific seismic belt and the Eurasian seismic belt. Earthquakes and volcanic eruptions occur frequently in the region. Statistics show that the seismic tsunami occurring in the circum-Pacific region accounts for 80% of the global tsunami. Nepal is an area where earthquakes and tsunamis are frequency. The reasons for the serious disasters caused by the tsunami are as follows: first, Palu Bay is a trumpet-shaped bay, the whole city is built around a narrow bay, so when the tsunami pours into the bay, it magnifies the impact of the tsunami; second, there are still problems in the early warning system of Indonesia's tsunami. After the earthquake, Indonesian authorities issued a tsunami warning, but the warning was lifted half an hour later, which did not play a tsunami warning role, causing many people to stay on the beach and fail to evacuate in time.

Table 2 List of earthquakes causing major tsunamis
4 MAIN FEATURES OF THE GLOBAL DISASTER EARTHQUAKE IN 2018

(1) The frequency of strong earthquakes was low in this year, and 18 earthquakes with M≥7.0 occurred. The number of casualties caused by earthquake disasters was also lower than the average of previous years.

(2) The relatively concentrated earthquake disasters were mainly caused by the earthquake in Papua New Guinea in the Pacific Rim earthquake zone, the earthquake in Indonesia and the earthquake in Hokkaido in Japan.

(3) Poor seismic performance and secondary disasters in disaster-stricken areas are the main factors of casualties. Several earthquakes that caused a large number of casualties this year (Babya New Guinea M7.5 earthquake, Indonesia M6.4 earthquake, Japan M6.6 earthquake, Indonesia M7.5 earthquake) caused by secondary disaster of earthquake, economic conditions, earthquake resistance of houses, etc. A relatively large number of casualties. The earthquake-resistant performance of houses in Papua New Guinea and Indonesia is poor. Most of the houses on the island are wooden buildings. There are no standardized building codes and seismic standards. In addition, the earthquake caused secondary disasters such as debris flows, landslides, tsunamis and so on, resulting in very serious casualties and economic losses.

5 SUGGESTIONS AND MEASURES FOR EFFECTIVELY RESPONDING TO EARTHQUAKE DISASTERS

(1) Improve the seismic fortification capability of buildings. From the earthquakes with large casualties in 2018, the proportion of casualties caused by the collapse of houses is relatively large. Therefore, it is of vital importance to enhance the seismic fortification capabilities of buildings such houses. Reasonable site selection, try to avoid the construction of houses in the fault area and the frequent occurrence of earthquakes. The structure of the building should pay attention to the role of the ring beam to make the building stable. It must meet the seismic fortification standards of the area, so as to improve the seismic fortification standards of the building, to reduce the number of casualties in the earthquake.

(2) Improve self-rescue ability. When an earthquake occurs, it is often necessary to take self-rescue measures before waiting for the rescue force to arrive, especially during the golden rescue time. Therefore, learning to make reasonable self-help is one of the important means to avoid casualties. The earthquake emergency kits should be kept in the home, and the awareness of earthquake prevention should be strengthened, also earthquake emergency drills should be participated and some measures and procedures for earthquake self-rescue should be familiar through emergency drills to improve self-rescue ability, thus effectively reducing earthquake casualties.

(3) Effectively respond to secondary disasters caused by earthquakes. Large earthquakes are often accompanied by secondary disasters. The secondary disasters such as fires, landslides, falling rocks, collapses and tsunamis are extremely harmful. Statistics show that the proportion of earthquake deaths caused by secondary disasters is large, which occurred in 2018. In several earthquakes, a tsunami was triggered, causing great casualties. Therefore, it is necessary to promptly eliminate the danger after the earthquake and evacuate the crowd as soon as possible to avoid unnecessary casualties caused by secondary disasters.

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