離開
進入《中英對照讀新聞》What Causes Earthquake Swarm? 「群震」的成因為何？
日本伊豆群島2000年曾發生大規模「群震」。圖為美國地質調查所2月11日觀測到伊豆群島地區發生芮氏規模4.8、震源深度10公里的地震。（取自網路）
◎劉宜庭
Seismic activities can be classified into either a major quake followed by aftershocks or an earthquake swarm. In general, within major earthquakes a maximum-scale quake is followed by a number of minor aftershocks. Meanwhile, the swarm earthquake is a series of the quakes of a similar scale to the mainshock.
地震活動大致可分為兩類，一次主震伴隨多次餘震，或是「群震」。大多數情況下，大地震發生時，規模最大的地震發生後，會有許多規模較小的餘震緊接而至。「群震」則是規模和主震相近的一系列地震。
The AD 2000 Izu islands earthquake that struck the northern Izu islands showed one of the most energetic swarms ever recorded. We analysed the seismicity data as well as the land survey of this swarm to demonstrate that the sustained crustal deformation and increase in stressing rate largely contribute to the occurrence of earthquake swarms.
西元2000年襲擊（日本）伊豆群島北部的伊豆群島地震，出現前所未見、最強勁的「群震」紀錄之一。我們分析該次地震活動數據，並進行田野調查，證實持續的地殼變形與應力增加，很大程度地導致「群震」發生。
Earthquake swarm has been considered to be "an exceptional phenomena" which differs from the normal earthquakes. Dominant hypotheses that explain the occurrence of the swarm include the immediate influence of magma and ground water (ex. intrusion to the fault), peculiar inhomogeneity of crustal structure and so on.
「群震」被視為不同於普通地震的「特殊現象」。解釋「群震」成因的主要假說，包括岩漿和地下水的直接影響（例如沿著斷層侵入）、特殊的非均質性地殼構造等。
新聞辭典
aftershock：名詞，餘震。例句：An aftershock is a smaller earthquake that occurs after a previous large earthquake, in the same area of the main shock.（「餘震」是指「主震」所在的相同區域內，在較大地震發生後出現的較小地震。）
mainshock：名詞，主震。例句：A foreshock is an earthquake that occurs before the mainshock.（「前震」指的是「主震」之前發生的地震。）
seismicity：名詞，地震活動。例句：The historic record of seismicity in California is too short to determine confidently how often large earthquakes reoccur.（加州的地震活動歷史紀錄期間太短，以至於無法確切得知大地震重複發生的頻率。）
