Deflation during caldera unrest: constraints on subsurface processes and hazard prediction from gravity–height data
Deflation during caldera unrest: constraints on subsurface processes and hazard prediction from gravity–height data
复制标题
火山口动荡期间的通货紧缩：对地下过程的限制和重力高度数据的危险预测
DOI：
10.1007/s00445-002-0212-7
复制
发表时间：
2002
影响因子：
3.5
通讯作者：
H. Rymer
中科院分区：
文献类型：
--
作者：
J. Gottsmann;H. Rymer
我们评估了Campi Flegrei、Kilauea、Askja和Krafla已公布的重力-高度（Δg/Δh）数据，以便区分火山口沉降过程中的地下过程。对于末端成员重力-高度相关性，如自由空气梯度（FAG）和布格校正自由空气梯度（BCFAG）， Δg/Δh梯度必须根据地下质量再分布、密度变化或这些的某种组合来解释。沉降区(1)沿或下方、(2)与FAG之间或(3)沿或上方沉降区（Δg/Δh）的梯度。我们根据火山沉降期间的地下过程对这三个区域进行了评价。我们将Δg/Δh梯度解释为火山活动前兆的可能指标，并提出重力-高度测量可能有助于探测岩浆排水引起的火山口崩塌前兆。在这种背景下，1875年冰岛的Askja火山爆发被重新解释为火山爆发的开始是由一个撤离的岩浆库的顶部坍塌引起的。基于近期火山顶板坍塌的其他例子，我们评估了重力-高度测量在评估火山口沉降期间火山风险方面的贡献。形成破火山口的喷发是环境和经济上最具破坏性的火山事件。通货膨胀通常被认为是经济活动的重要前兆。在这里，我们表明通货紧缩可能与破火山口形成爆炸喷发的触发机制有关。
We have evaluated published gravity–height (Δg/Δh) data on Campi Flegrei, Kilauea, Askja and Krafla, in order to discriminate between subsurface processes during caldera subsidence. With respect to end member gravity–height correlations, such as the free air gradient (FAG) and the Bouguer corrected free air (BCFAG), Δg/Δh gradients must be interpreted in terms of subsurface mass redistribution, density changes or some combination of these. Δg/Δh gradients during subsidence plot (1) along or below the BCFAG, (2) between the BCFAG and the FAG or (3) along or above the FAG. We have evaluated each of these three regions in terms of subsurface processes during volcano subsidence. We have interpreted Δg/Δh gradients as possible indicators of precursors of volcanic activity and propose that gravity–height surveys may help to detect precursors of caldera collapse caused by magma drainage. In this context, the 1875 eruption of Askja in Iceland has been re-interpreted in terms of the beginning of the eruptive episode being induced by roof collapse of an evacuating magma chamber. Based on other examples of recent volcanic roof collapses, we evaluate the contribution of gravity–height surveys in assessing volcanic risks during caldera subsidence. Caldera-forming eruptions are environmentally and economically the most devastating volcanic events. Inflation is usually considered to be an important precursor to activity. Here, we show that deflation may be associated with the trigger mechanism for caldera-forming explosive eruptions.