中文摘要：

对2015年尼泊尔MS8.1地震的地壳均衡背景及其引起的地表形变特征进行了研究,结果表明：（1）尼泊尔MS8.1地震震中以南的印度板块岩石圈有效弹性厚度大约为9km,加载主要来自地幔;地震以北的拉萨地块岩石圈有效弹性厚度大约为2km,加载主要来自地表.（2）尼泊尔MS8.1地震震中以南地区的地壳均衡异常大约为-100mGal（10-5 m·s-2）,但其北部的地壳均衡异常则为300~400mGal,尼泊尔MS8.1地震发生在地壳均衡负异常向正异常过渡的高梯度带上.（3）尼泊尔MS8.1地震使震中周围地区的地壳整体向南运动,最大水平位移超过1.5m,分布在震中东南.震中以北的同震垂向位移总体为负值,最大下降幅度超过0.5m,同震重力变化总体为正值,最大超过60μGal（10-8 m·s-2）;震中以南的垂向位移总体为正值,最大升幅超过0.7m,同震重力变化总体为负值,最大降幅超过-120μGal.（4）尼泊尔MS8.1地震使＂世界屋脊＂喜马拉雅山脉产生沉降,最大同震降幅超过120mm,震后松弛效应将使＂世界屋脊＂持续缓慢下降.该强震使世界最高峰珠穆朗玛峰降低了2~3mm,有可能被GPS、InSAR等现代大地测量工具检测到.

英文摘要：

We studied the gravitational isostasy background and the surface deformation response characteristics of the 2015 Nepal MS8.1earthquake.The results showed that：（1）the lithosphere effective elastic thickness of Indian block,an area south to the epicenter of 2015 Nepal MS8.1earthquake,is about 9 km,and the load comes mainly from the mantle. However,the lithosphere effective elastic thickness of Lhasa block,an area north to the great earthquake,is about 2km,and the load comes mainly from the tomography.（2）The gravitational isostasyanomalies are about-100 mGal（10-5 m·s-2）at area south to the Nepal MS8.1earthquake,while at area north to the earthquake,the values become 300~400 mGal.The Nepal MS8.1earthquake occurred at a high gradient belt where the isostasy varies from negative anomalies to positive anomalies.（3）Due to the Nepal MS8.1earthquake,the earth surface around the epicenter moved southward as a whole.The maximum of the co-seismic horizontal displacements is above 1.5m,located at the area southeast to the epicenter.At the area north to the epicenter,the co-seismic vertical displacements are negative and the maximum exceeds-0.5m,the gravity changes are positive and the maximum is above 60μGal（10-8 m·s-2）.However,the values at the area south to the epicenter are vice versa.The maximum co-seismic vertical displacements and gravity changes are 0.7mand-120μGal respectively.（4）The Nepal MS8.1earthquake made the roof of the world,the Himalayas,decease as a whole,and the maximum decrease magnitude is more than 120 mm.It is expected the Himalayas will continue to decrease because of the relaxation effects of the mantle.The Nepal MS8.1earthquake made Mt.Everest decrease about2~3mm,which may be detectable by modern measuring tool such as GPS and InSAR.