Merging eruption datasets: building an integrated Holocene eruptive record for Mt Taranaki, New Zealand
Merging eruption datasets: building an integrated Holocene eruptive record for Mt Taranaki, New Zealand
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合并喷发数据集：为新西兰塔拉纳基山建立完整的全新世喷发记录
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发表时间：
2009
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通讯作者：
R. Stewart
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作者：
M. Turner;M. Bebbington;S. Cronin;R. Stewart
获取详细的火山喷发频率数据集的火山系统是现实的火山喷发预测。然而，即使有一个或多个日期明确的喷发记录，准确的数据集也很难汇编。一个单一的记录通常低于代表喷发频率，而结合两个或多个记录可能会导致过度代表。虽然玻璃组合物已被证明是成功的主要流纹岩火山灰的火山灰年代学研究，微晶生长和薄玻璃碎片抑制其应用于安山质火山灰。一种方法，包括一个组合的两种技术相关联的同喷发沉积物的数据从典型的安山成层火山的山。新西兰塔拉纳基。首先，使用放射性碳年龄和每个事件的相关误差来识别暂定匹配。其次，钛磁铁矿微斑晶的成分被用作独立检查，并且在有年龄数据的情况下被证明是一个有用的相关工具。使用两个湖芯记录火山灰层在重叠的时间框架，放射性碳年龄相关程序建议31火山灰匹配。其中15对有地球化学数据。在其中三种情况下，钛磁铁矿的成分不匹配。因此，这些“成对”的火山岩来自成分不同的岩浆，因此可能代表不同的事件。根据更好的地球化学配对，在测年程序的时间不确定性范围内重新分配了另外三个匹配项。最后的综合数据表明，从塔拉纳基开始，在公元前96年到10 150年之间，至少有138次单独的火山灰喷发。使用组合数据集的混合威布尔更新模型预测的概率为0.52的喷发发生在未来50年在这座火山。目前的年喷发概率估计为1.6%。这种可能性几乎是依靠单一地层记录获得的可能性的两倍。
Acquiring detailed eruption frequency datasets for a volcano system is essential for realistic eruption forecasts. However, accurate datasets are inherently difficult to compile, even if one or more well-dated eruption records are available. A single record typically under-represents the eruption frequency, while combining two or more records may result in an overrepresentation. Although glass compositions have proven to be successful in tephrochronological studies of dominantly rhyolitic tephras; microlitic growth and thin glass shards inhibit their application to andesitic tephras. A method consisting of a combination of two techniques for correlating syn-eruptive deposits is demonstrated on data from the typical andesitic stratovolcano of Mt. Taranaki, New Zealand. Firstly, tentative matches are identified using the radiocarbon age and associated error of each event. Secondly, the compositions of titanomagnetite micro-phenocrysts are used as an independent check, and shown to be a useful correlation tool where age data is available. Using two lake-core records containing tephra layers in an overlapping time-frame, the radiocarbon age-correlation procedure suggested 31 tephra matches. Geochemistry data were available for 15 of these pairs. In three of these cases, the titanomagnetite compositions did not match. Hence, these “paired” tephras were from compositionally distinct magmas and therefore likely represent separate events. An additional three matches were reassigned within the temporal uncertainty limits of the dating procedure, based on better geochemical pairing. The final combined dataset suggests that there have been at least 138 separate ash fall-producing eruptions between 96 and 10 150 years B.P. from Taranaki. Using the combined dataset the mixture of Weibulls renewal model forecasts a probability of 0.52 for an eruption occurring in the next 50 years at this volcano. The present annual eruption probability is estimated at 1.6%. This likelihood is almost double that obtained when relying on a single stratigraphic record.