CHARACTERISTICS OF SEISMIC-WAVES COMPOSING HAWAIIAN VOLCANIC TREMOR AND GAS-PISTON EVENTS OBSERVED BY A NEAR-SOURCE ARRAY
CHARACTERISTICS OF SEISMIC-WAVES COMPOSING HAWAIIAN VOLCANIC TREMOR AND GAS-PISTON EVENTS OBSERVED BY A NEAR-SOURCE ARRAY
复制标题
DOI：
10.1029/90jb02781
复制
发表时间：
1991-04-10
期刊：
影响因子：
--
通讯作者：
CHOUET, B
中科院分区：
文献类型：
--
作者：
FERRAZZINI, V;AKI, K;CHOUET, B
一个相关的方法，专门设计用于描述一个复杂的波场的特性，适用于火山地震和气体活塞事件的地球观测系统仪器的半圆形阵列设置在普乌火山口的脚下的东裂谷的基拉韦厄火山，夏威夷。作为频率的函数，在整个阵列的三个组件的运动的相关系数的空间模式是类似的气体活塞事件和震颤，并清楚地描绘了分散波传播的阵列从Puu Oo的方向。波场由数量相当的瑞利波和洛夫波组成，它们以相似且极慢的相速度传播，相速度范围从2 Hz时的700 m/s到8 Hz时的300 m/s。高度破裂的凝固熔岩流上部署的阵列，和subjacent结构的交替熔岩和火山灰层形成的Puu Oo自1983年以来反复喷发，似乎是负责观察到的低速度。普乌的结果与1976年在部分凝固的基拉韦厄火山伊基熔岩湖上进行的实验结果形成鲜明对比。在基拉韦厄伊基没有观测到瑞利波，但观测到发达的勒夫波列在那里传播，其速度是普乌附近观测到的速度的两倍。这两个地点表面波传播特性的差异可能是由于基拉韦厄伊基存在一个熔融岩石的软水平层，这可能降低了瑞利波的相速度，比洛夫波更剧烈，导致瑞利波模式的严重散射。另一方面，在Puu Oo我们的阵列下的薄的浅表帕霍流可能有利于在该位置比在基拉韦厄伊基更广泛地发展垂直柱状节理，这可能降低了控制Love波模式的剪切模量。在普乌发现的2至5赫兹的频带中的平均相速度大致类似于堪察加半岛Klyuchevskoy火山的震颤，但频率依赖性似乎更强的普乌乌。
A correlation method, specifically designed for describing the characteristics of a complex wave field, is applied to volcanic tremor and gas-piston events recorded by a semicircular array of GEOS instruments set at the foot of the Puu Oo crater on the east rift of Kilauea volcano, Hawaii. The spatial patterns of correlation coefficients obtained as functions of frequency for the three components of motion over the entire array are similar for gas-piston events and tremor, and clearly depict dispersive waves propagating across the array from the direction of Puu Oo. The wave fields are composed of comparable amounts of Rayleigh and Love waves propagating with similar and extremely slow phase velocities ranging from 700 m/s at 2 Hz to 300 m/s at 8 Hz. The highly cracked solidified lava flow on which the array was deployed, and subjacent structure of alternating lava and ash layers formed during repeated eruptions of Puu Oo since 1983, appear to be responsible for the low velocities observed. The results from Puu Oo stand in sharp contrast to those obtained in an experiment conducted in 1976 on the partially solidified lava lake of Kilauea Iki. Rayleigh waves were not observed in Kilauea Iki, but well-developed trains of Love waves were seen to propagate there with velocities twice as high as those observed near Puu Oo. These differences in the propagation characteristics of surface waves at the two sites may be attributed to the presence of a soft horizontal layer of molten rock in Kilauea Iki, which may have lowered the phase velocity of Rayleigh waves more drastically than that of Love waves, resulting in severe scattering of the Rayleigh wave mode. On the other hand, the thin superficial pahoehoe flow under our array at Puu Oo may have favored the development of vertical columnar joints more extensively at this location than at Kilauea Iki, which may have reduced the shear moduli controlling the Love wave mode. The average phase velocities in the frequency band from 2 to 5 Hz found at Puu Oo are roughly similar to those determined for tremor at Klyuchevskoy volcano, Kamchatka, but the frequency dependence appears much stronger at Puu Oo.