Short-term and imminent geomagnetic anomalies of the Wenchuan Ms8.0 earthquake and exploration on earthquake forecast

• 来源期刊: 地震学报（英文版）
• 学科: 地球科学
• 年，卷（期）: 2009,（2）
• 页码范围: 135-141
• 页数: 7页
• 分类号: P315.75
• 语种: 英文
• DOI: 10.1007/s11589-009-0135-x

摘要

The diurnal variation of the geomagnetic vertical component is exhibited mainly by changes of phase and amplitude before strong earthquakes. Based on data recorded by the network of geomagnetic observatories in China for many years, the anomalous features of the appearance time of the minima of diurnal variations (i.e, low-point time) of the geomagnetic vertical components and the variation of their spatial distribution (i.e, phenomena of low-point displacement) have been studied before the Wenchuan Ms8.0 earthquake. The strong aftershocks after two months' quiescence of A/6 aftershocks of the A/s8.0 event were forecasted based on these studies. There are good correlativities between these geomagnetic anomalies and occurrences of earthquakes. It has been found that most earthquakes occur near the boundary line of sudden changes of the low-point time and generally within four days before or after the 27th or 41st day counting from the day of the appearance of the anomaly. In addition, the imminent anomalies in diurnal-variation amplitudes near the epicentral areas have also been studied before the Wenchuan earthquake.