中米の火山地震帯

Tectonic Setting: The Cocos Plate Under Central America

Central America sits above one of the most tectonically active settings in the Western Hemisphere, where the Cocos Plate subducts beneath the Caribbean Plate along the Middle America Trench, which runs roughly parallel to the Pacific coast of Mexico, Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica, and Panama. This 沈み込み帯1枚のプレートがもう1枚のプレートの下にもぐり込み、マントルへと沈み込む領域。沈み込み帯は世界最大級の地震（M8.5以上）を引き起こし、深い海溝や火山弧を伴う。 occurs at rates of approximately 7 to 9 centimeters per year, making it one of the fastest subduction systems in the world, and it generates both frequent seismic activity along the interface and 火山性地震マグマの移動、ガス圧、または火山付近の岩石の破砕によって引き起こされる、火山活動に関連する地震。群発することが多く、噴火の前兆となる場合がある。 activity associated with the volcanic arc built above the subducting plate.

The Central American Volcanic Arc is a chain of approximately 500 volcanoes — roughly 40 of which are considered active — extending from Guatemala through Costa Rica. Volcanic activity and 火山性地震マグマの移動、ガス圧、または火山付近の岩石の破砕によって引き起こされる、火山活動に関連する地震。群発することが多く、噴火の前兆となる場合がある。 swarms are constant features of the regional landscape, with several volcanoes (Santiaguito in Guatemala, Santa Ana in El Salvador, Arenal and Turrialba in Costa Rica) in near-continuous eruption or heightened activity at any given time. The distinction between tectonic earthquakes on the 沈み込み帯1枚のプレートがもう1枚のプレートの下にもぐり込み、マントルへと沈み込む領域。沈み込み帯は世界最大級の地震（M8.5以上）を引き起こし、深い海溝や火山弧を伴う。 interface, earthquakes within the subducting slab, and 火山性地震マグマの移動、ガス圧、または火山付近の岩石の破砕によって引き起こされる、火山活動に関連する地震。群発することが多く、噴火の前兆となる場合がある。 events driven by magmatic processes is critical for hazard assessment but requires careful seismological analysis to resolve.

Volcanic Earthquakes: A Distinct Hazard

火山性地震マグマの移動、ガス圧、または火山付近の岩石の破砕によって引き起こされる、火山活動に関連する地震。群発することが多く、噴火の前兆となる場合がある。 activity in Central America is generated by multiple mechanisms including the pressurization of hydrothermal systems beneath volcanoes, the movement of magma through conduits and reservoirs, the collapse of volcanic edifices, and the interaction between rising magma and fracture systems. These events can range from the harmless background 火山性地震マグマの移動、ガス圧、または火山付近の岩石の破砕によって引き起こされる、火山活動に関連する地震。群発することが多く、噴火の前兆となる場合がある。 swarms that accompany continuous degassing activity to large, damaging earthquakes triggered by volcanic processes. The 2001 El Salvador earthquakes (two events of magnitude 7.7 and 6.6) were tectonic rather than volcanic in origin but occurred in a volcanic region, and subsequent analysis of slope stability in volcanic ash deposits was critical for understanding the devastating 地震誘発地すべり地震の揺れによって引き起こされる、土砂や岩石の斜面下方への移動。地すべりは地域全体を埋没させることがあり、揺れそのものより多くの犠牲者を出すこともある。 damage.

The 環太平洋火山帯世界の地震のおよそ90%が発生する、太平洋を取り囲む馬蹄形の地帯。総延長は40,000kmに及び、452の火山を含む。 position creates a setting where earthquakes, volcanic eruptions, and their 二次的地震災害揺れそのものではなく、揺れによって引き起こされる災害——津波・地すべり・液状化・火災・ダム決壊・化学物質の流出などを指す。揺れそのものより大きな被害をもたらすことが多い。 are constantly present. Costa Rica's Turrialba volcano has periodically disrupted aviation across Central America and deposited volcanic ash across agricultural areas. Guatemala's Santiaguito volcano regularly generates lahars that travel down river valleys toward populated areas. The compound nature of volcanic-seismic hazard in Central America means that civil protection agencies must simultaneously monitor multiple ongoing processes rather than simply waiting for discrete large events.

Historical Seismicity: Recurring Catastrophes

The 1972 Managua Earthquake (magnitude 6.2) struck the Nicaraguan capital at midnight on December 23, killing between 5,000 and 10,000 people in a city of 400,000 and causing the complete collapse of the central business district. The earthquake essentially destroyed downtown Managua so thoroughly that the city was never fully rebuilt in the original location, with government functions and commercial activity gradually relocating to suburban areas. The combination of the earthquake's direct impact and the corrupt management of international relief funds by the Somoza government became a significant factor in the political upheaval that followed.

The 1986 El Salvador Earthquake (magnitude 5.7) killed approximately 1,000 people in San Salvador, demonstrating once again the extreme vulnerability of Central American urban construction to even moderate earthquakes. The 2001 El Salvador earthquake sequence, the 2009 Costa Rica earthquake (magnitude 6.1), the 2012 Guatemala earthquake (magnitude 7.4), and the 2012 Costa Rica earthquake (magnitude 7.6) are among many events reflecting the 環太平洋火山帯世界の地震のおよそ90%が発生する、太平洋を取り囲む馬蹄形の地帯。総延長は40,000kmに及び、452の火山を含む。 setting's relentless generation of seismic energy.

Building Vulnerability and Poverty

Central America's earthquake losses are disproportionately high relative to earthquake size because of the widespread use of 無補強組積造（URM）鉄筋補強のないレンガまたはブロック造の建物で、地震の揺れに極めて脆弱である。URM建物は、世界の地震死者数の大部分を占める。 construction in highly 沈み込み帯1枚のプレートがもう1枚のプレートの下にもぐり込み、マントルへと沈み込む領域。沈み込み帯は世界最大級の地震（M8.5以上）を引き起こし、深い海溝や火山弧を伴う。-exposed countries where poverty limits investment in earthquake-resistant building. Adobe construction in Guatemala's highlands, brick masonry in El Salvador and Nicaragua, and poorly reinforced concrete in urban areas throughout the region represent a legacy of construction that performs poorly in earthquakes. Use Seismic Risk Checker to understand how Central American cities compare in terms of ground acceleration hazard relative to their 耐震基準建物の最低限の耐震安全性を確保するための、設計・建設に関する法的要件の体系。大地震で新たな脆弱性が明らかになるたびに更新される。 standards.

Costa Rica represents a somewhat contrasting case: the country has invested more consistently in 耐震基準建物の最低限の耐震安全性を確保するための、設計・建設に関する法的要件の体系。大地震で新たな脆弱性が明らかになるたびに更新される。 development and enforcement than most Central American neighbors, and its earthquake performance record, while still involving casualties, is generally better than comparable events elsewhere in the region. The Costa Rican Federation of Engineers and Architects (CFIA) maintains actively updated seismic code provisions based on regular review of scientific developments.

What Makes Central America Unique

Central America's earthquake risk is inseparable from its volcanic character and its economic development challenges. The 環太平洋火山帯世界の地震のおよそ90%が発生する、太平洋を取り囲む馬蹄形の地帯。総延長は40,000kmに及び、452の火山を含む。 沈み込み帯1枚のプレートがもう1枚のプレートの下にもぐり込み、マントルへと沈み込む領域。沈み込み帯は世界最大級の地震（M8.5以上）を引き起こし、深い海溝や火山弧を伴う。 that creates its extraordinary biodiversity, dramatic volcanic landscapes, fertile soils from volcanic ash, and geothermal energy resources also generates the earthquakes and eruptions that periodically devastate communities. The region's earthquake risk is a product of extreme tectonic hazard combined with housing stock vulnerability born of poverty — a combination that produces some of the highest per-capita earthquake death rates in the Western Hemisphere from events that would cause far fewer casualties in richer, better-built nations.