Earthquakes
Indonesia's Earthquakes
Earthquake Risks in Indonesia
Indonesia's geographical location along the boundaries of four major tectonic plates namely the Eurasian, Indo-Australian, Pacific and Philippine Sea plates accounts for the restive seismic activity in the region.
The map below illustrates the earthquake risk zone map of Indonesia. The risk increases from a minimum risk (Zone I) to a maximum risk (Zone V).
Earthquake Intensity
The map below shows the countless earthquakes that struck Indonesia since the start of the 20th century. These seismic activities in Indonesia and the surrounding area provides crucial evidence for the active tectonic processes of this region. The bigger the circle, the higher the magnitude of the earthquake in the Richter Scale. The lone black circle represents the most destructive earthquake, the indian Ocean Earthquake of 2004, that devastated the country in its modern history.
Indonesia's Active Faults
The known principal zones of active faulting in Indonesia comprise several strike-slip
fault belts (Sumatra fault zone, 1600 km long; Palu-Koro fault zone, 700 km long ; Irian
fault zone that on land is 1300 km long); the central depression of Timor where normal
faulting is associated with lateral displacements; the Banyumas depression of Java; active
volcanoes (with records from Tangkubanperahu, Merapi, Kelut all in Java and Krakatau
in Sunda Strait), where principally normal faulting takes place through tectono-gravity
causes; extensive limestone terrains (Gunung Sewu, Java ; Maros area. South Sulawesi;
Ayamaru plateau, Irian Jaya) where normal faulting occurs through undermining.
The fault that has been an area of concern is the Great Sumatran Fault, which is a strike-slip fault that extends the entire length of Sumatra and coincides geographically with the Sunda volcanic arc. The fault is heavily segmented, with most segments less than 100 km long. Earthquake in Sumatra has multiple sources including thrust earthquakes on the subduction fault, strike-slip earthquakes on the Sumatran fault, volcanic quakes and deeper earthquakes within the subducting lithosphere.
Situated off the west coast of Java in Indonesia, the Sumatra fault has been home to some of the most powerful earthquakes the world has ever seen. In 2004, a magnitude 9.1 quake caused a tsunami that devastated shorelines across the Indian Ocean, claiming close to a quarter million lives. In March of 2005, another earthquake struck, this time 8.7. In September 2007, two more, 8.4 and 7.9, hit within 12 hours of one another.
Impacts of Indonesia's Earthquakes
Earthquakes are one of the largest threats from moving plate tectonics in Indonesia as they come sudden and can strike in densely populated areas, such as the bigger cities. Earthquakes with a magnitude of around five or six on the Richter Scale happen almost on a daily basis in Indonesia but usually cause no or little damage. When the magnitude becomes over seven on the scale however, an earthquake can potentially do a lot of damage. Yearly, two or three earthquakes with a magnitude of seven or higher occur in Indonesia and cause casualties and damage to the infrastructures of the country or to the environment.
The maps below indicate locations of earthquake disasters in Indonesia. The size of circles represents the scale of the disasters in terms of human and economic losses. Since 1977, 24 earthquakes with magnitude of 8 or more have been recorded in and around Indonesia. The 2004 Indian Ocean Earthquake (M9.1) was the largest. More than 1,000 people were killed in 7 of those earthquakes. Additionally 10,000 people were killed by the earthquakes that occurred in 1815 and 1917 in Bali. The earthquake that greatly impacted the Indonesian economy were the 2004 Indian Ocean Earthquake (M9.1), the 2006 Central Java Earthquake, and the 2009 Sumatra Earthquake (M7.5).
Human Losses
Economic Losses
Earthquake Risk Reduction and Mitigation
Indonesia is located along the Pacific Ring of Fire and faces many natural threats including earthquakes, tsunamis, volcanic eruptions, flooding, and droughts. The country records upwards of 3,000 natural disasters across the country in any given year. On average, 90% or more of these events are hydro-meteorological (e.g., storms, tornadoes, and floods); however, the remainder of events – earthquakes and tsunamis – are usually more deadly and more damaging. In any given decade, the country can suffer disaster events that cost thousands of lives and displace tens of thousands of people while the economic losses can total US$3 billion annually.
Recent efforts in Indonesia to mitigate the impacts of earthquake hazards focus on the interplay of bureaucratic policy, scientific research, and community preparedness.
- In an effort to prevent future devastating impacts such as those caused by the 2004 Indian Ocean earthquake and the tsunami that ensued, Indonesia has passed Law 24/2007 on Disaster Management and created the National Agency for Disaster Management and the Local Agency for Disaster Management.
- The government of Indonesia invests about 1-2% of its budget into disaster risk and reduction ranging between $0.7 and $1 billion for every fiscal year with a general upward trend of funding. The majority of the money allocated to DRR is being used for physical disaster risk reduction. This includes updating infrastructure to be disaster resilient and creating disaster mitigation infrastructure.
- Indonesia's geological agency, the Centre for Volcanology and Geological Hazard Mitigation, is tasked to monitor active fault lines; update seismic hazard maps; revise and continuously update building and infrastructure codes for bridges, dams, harbors, and other special structures; develop microzonation maps for big cities like Jakarta; develop an academic draft of the Indonesian Earthquake Master Plan; develop design guidelines for tsunami vertical evacuation; and to establish the Indonesia National Research Center for Earthquake (initiated in June 2016).
- Geologic hazard socialization has been adopted in recent years. Socialization is focused on communities who live in geological hazard zones, the objective of which is to enhance awareness and knowledge for communities for preparation and evacuation measures in the event of an earthquake.
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Very good seismic reflection!- It is good to see they have lots of mitigation measures in place, as they are very active seismically.
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