台灣地區全磁場時空變化之研究(1989-2004年)

Study of Total Magnetic Field in Temporal and Spatial Variations in Taiwan (1989 ~ 2004)

陳界宏(Chieh-Hung Chen)

指導教授 ： 顏宏元

國立中央大學/地球科學學院/地球物理研究所/博士(2005年)

摘要

本論文主要的目的是詳細探討台灣地區的地磁場變化。時間場方面：(1)探索台灣地區地磁場與國際地磁參考場(IGRF)之間的差異。並說明於2000年以後的地磁參考場修正必須要使用IGRF-9的原因。(2)分析台灣地區地磁異常現象與地震發生之相關性。利用小區域的地磁場差異度較小的特性，研究地震引發地磁異常變化。地震的規模越大所導致的地磁異常越強，而當地磁異常停止增強表示大地震即將發生。結果顯示距震央50公里以內的觀測站可以偵測到地震所引發的異常現象，因此對於地震所發生的規模、時間和地點都可以做出一定程度的推估。

空間場方面：利用台灣磁力普測資料，建立完整的地磁資料處理流程。由磁力異常圖獲知，西部的磁力異常較中央山脈高，推測為西部紅土台地的磁感率高於中央山脈的變質岩區。台灣西南部的磁力異常高區可能因弧後的地熱活動所造成。

地震稀少帶均位於磁力異常圖中的高區，推測地下可能存在鐵質物質；而於磁性基盤面中位於基盤的高區或是基盤起伏較為平緩的地區；於居禮溫度面中四個地區的居禮溫度面較深。因此台灣的地震稀少帶最主要的組成應該是較冷且堅硬的岩層。這和一般認為因為地下較高的溫度而讓岩層產生塑性不易斷裂的想法不同。

關鍵字

地磁場 ； 地震預測 ； 磁力普測

並列摘要

Studying the variation of geomagnetic field in Taiwan is the main purpose in this dissertation. From the temporal aspect: (1) The difference between the geomagnetic filed of Taiwan and IGRF has been studied, and the reason why the geomagnetic reference field can be replaced by IGRF-9 after 2000 has been also elucidated. (2) The relationship between the geomagnetic anomalies and earthquake occurrence has been analyzed. By comparing daily variations of geomagnetic field in a small area, the anomalies could be found in the record at the station which is within a distance of 50km from the epicenter both before and after the large earthquake. The earthquake occurs when the increase of the anomaly strength in the geomagnetic field stops. Therefore, it is possible to estimate roughly three important parameters of the coming earthquake, i.e. magnitude, occurrence time and location.
On the other hand, from the spatial aspect, a completed procedure of data processing has been set up to obtain the magnetic anomaly map for Taiwan region. Based on this map, the susceptibility of lateritic layer in the western part of Taiwan is larger than that for the metamorphic rock in the Central Range. The high magnetic anomaly is caused by the heat activity at the back-arc region in southwestern Taiwan. The areas with positive magnetic anomaly and stable magnetic basement suggesting the existence of iron-rich rocks and deep Curie temperature surface indicating low temperature zone may be related with four aseismic areas.

並列關鍵字

geomagnetic survey ； earthquake prediction ； geomagnetic field

參考文獻

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