Duration-amplitude scaling of volcanic tremor recorded at Mt. Erebus volcano, Antarctica;Duration-amplitude scaling of volcanic tremor recorded at Mt. Erebus volcano, Antarctica

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題名:	Duration-amplitude scaling of volcanic tremor recorded at Mt. Erebus volcano, Antarctica;Duration-amplitude scaling of volcanic tremor recorded at Mt. Erebus volcano, Antarctica
作者:	安蒂美 Ardiani, Mei Astrid
貢獻者:	國立中央大學
關鍵詞:	Duration-amplitude scaling of volcanic tremor recorded at Mt. Erebus volcano, Antarctica;Duration-amplitude scaling of volcanic tremor recorded at Mt. Erebus volcano, Antarctica
日期:	2018-07-18
上傳時間:	2018-08-31 13:21:54 (UTC+8)
摘要:	自然界中的大多數現象都和其數量和規模有關，我們可以利用這種關係來釐清其發展的過程。在這個研究中，我們調查了2002年5月至2004年4月在南極Erebus火山記錄的278次震顫事件的持續時間與振幅的分佈。我們計算減少的位移（DR）來統一數據，以獲得其持續時間和幅度的數值。在實驗中，我們使用了兩種比例模型，分別是指數律及冪定律。我們以決定係數（R2）和卡方檢驗（X2）來測試數據在兩種模型中的狀況。其中有270次震顫事件符合指數律，8次震顫事件符合冪律模型。對於這8次震顫事件，冪定律行為可以用兩種方式來解釋：它們起源的過程不受規模限制，它們可能被噪訊所影響。接著，我們將這270件符合指數律的震顫事件進行頻譜分析，然後將這些震顫分為以下三組：（1）諧波震顫，（2）寬帶震顫和（3）諧波和寬帶震顫之間的混合。為了確定這些震顫的震源大小，我們以柯史二樣本檢定Two-sample Kolmogorov-Smirnov（KS）來檢驗。該測試利用特徵振幅的分佈作為來自上述組的所有震顫的指數擬合的結果。結果顯示，諧波震顫和寬帶震顫具有相同的特徵振幅分佈。因此，諧波和寬帶震顫具有相同的震源尺寸，而混合震顫則有不同的震源尺寸。震源尺寸有兩個明顯的長度不同，一個用於寬頻諧波震顫組，另一個用於混合震顫組。我們認為，在管道系統中，在不平滑表面附近所產生的氣泡雲振盪，可視為固定比例震顫事件起源的一大可能。這一機制也與前面的觀察結果一致：震動的產生，起因於管道系統內凹凸不平處所積聚的氣體，氣體在過程中形成氣囊，而後上升至熔岩湖表面。;Most phenomena in nature show a relationship between their numbers and their sizes. This relationship can be used to identify their source processes. In this respect, we investigate duration-amplitude distribution for 278 tremor events during May 2002-April 2004 recorded at Erebus volcano, Antarctica. We compute reduced displacement (DR) to normalize the data, and then obtain the duration and amplitude. In order to check their relationship, two models of scaling have been used. These models are exponential and power law. Coefficient of determination (R2) and chi-squared (X2) test are used to see how the data fit with the models. A total of 270 tremor events fit with an exponential law and eight tremor events fit with a power law model. For these eight tremor events, power law behavior can be explained in two ways: their source processes are not scale bounded and they might be corrupted by noise. Then, we examine 270 tremor events, which fit with exponential law. We perform spectral analysis, then classify these tremors into three groups: (1) harmonic tremor, (2) broadband tremor and (3) mixed between harmonic and broadband tremor. In order to determine the source size of these tremors, a statistical test called two-sample Kolmogorov-Smirnov (KS) test is performed. This test utilizes the distribution of characteristic amplitude as a result of exponential fitting of all the tremors from the aforementioned groups. The results show that harmonic tremor and broadband tremor have the same distribution of characteristic amplitude. Therefore, harmonic and broadband tremor share the same source size, while mixed tremor has a different one. There are two characteristic lengths of the source sizes, one for broadband-harmonic tremor groups, another for mixed tremor group. Oscillations of bubble clouds near the asperities of plumbing system, which represents a scale-bounded source process, is proposed as the plausible source of these tremor events. This mechanism also agrees with a former observation which stated that tremor generation requires accumulation of gas near localized asperities within the plumbing system before ascending to the lava lake as gas slugs.
顯示於類別:	[地球物理研究所] 博碩士論文

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