Yokoyama Izumi
Department of Pharmacology, Gunma University School of Medicine, Maebashi, Gunma 371-8511.
Proc Jpn Acad Ser B Phys Biol Sci. 2006 May;82(3):121-6. doi: 10.2183/pjab.82.121.
Pozzuoli is located at the center of the Campi Flegrei caldera, near Naples and is famous for its anomalous subsidence and upheaval documented since the Roman period. Its secular and gradual subsidence can be interpreted as self-loading compaction of the caldera fills while abrupt upheavals are geologically suspected to be caused by magmagenic movements or steam forces. In order to interpret the origin and the process of the Pozzuoli upheavals, they are compared with active volcanisms represented by the 1977-1982 eruption of Usu volcano in Hokkaido. Usu volcano outburst in 1977 in major pumice eruptions and repeated magmatic and phreatomagmatic eruptions, and manifested remarkable ground deformations accompanying earthquake swarms. In 1969, the ground of Pozzuoli began to upheave with increases in seismicity but finally failed to cause any eruptive phenomena at the surface; nevertheless there are common characteristics of their motives and processes between the two events. The motive of the Usu deformation is clearly due to magma movements while that of the Pozzuoli upheaval has not been completely settled. A quantitative relationship between seismicity and deformation gives a clue for discussing the motive of the Pozzuoli deformations. The discharge rates of seismic energy and the deformation rates are compared between the two events and a certain similarity is found. This suggests that the origin of the Pozzuoli event may be partly magmatic as well as the Usu eruption, but its behavior largely depends on the property of the caldera deposits. When their deformation volumes are taken into consideration, their characteristics become quantitatively conspicuous. The ground at Pozzuoli is much more easily deformed by the upward motive force than Usu volcano. This is due to the rheological property of the caldera deposits of Campi Flegrei, and agrees to the theory that interprets the secular subsidence observed in historical times, as self-loading compaction. It is interesting that there is a point of contact between anomalous movements of the ground along the seashore in Italy and remarkable magmatic movements at the active volcano in Japan.
波佐利位于那不勒斯附近的弗莱格雷火山口中心，以自罗马时期就有记载的异常沉降和隆起而闻名。其长期的逐渐沉降可解释为火山口填充物的自重压实，而突然的隆起在地质上被怀疑是由岩浆活动或蒸汽力量引起的。为了解释波佐利隆起的起源和过程，将其与以1977 - 1982年北海道有珠火山喷发为代表的活火山活动进行了比较。有珠火山在1977年爆发了大规模浮石喷发以及多次岩浆和蒸汽岩浆喷发，并伴随着地震群出现了显著的地面变形。1969年，波佐利的地面开始隆起，地震活动增加，但最终未能在地表引发任何喷发现象；然而，这两个事件在动机和过程上有共同特征。有珠火山变形的动机显然是由于岩浆活动，而波佐利隆起的动机尚未完全确定。地震活动与变形之间的定量关系为讨论波佐利变形的动机提供了线索。比较了这两个事件的地震能量释放率和变形率，发现了一定的相似性。这表明波佐利事件的起源可能部分与有珠火山喷发一样是岩浆成因的，但其行为在很大程度上取决于火山口沉积物的性质。当考虑它们的变形量时，它们的特征在数量上变得更加明显。波佐利的地面比有珠火山更容易因向上的动力而变形。这是由于弗莱格雷火山口沉积物的流变特性，并且与将历史时期观测到的长期沉降解释为自重压实的理论相符。有趣的是，意大利沿海地面的异常运动与日本活火山的显著岩浆活动之间存在联系。
