This paper deals with the interpretation of Bouguer gravity anomalies measured along a 250 km long Suhaitu-Etuokeqi gravity profile located at the transitional zone of the Alxa and Ordos blocks where geophysical chara...This paper deals with the interpretation of Bouguer gravity anomalies measured along a 250 km long Suhaitu-Etuokeqi gravity profile located at the transitional zone of the Alxa and Ordos blocks where geophysical characteristics are very complex. The analysis is carried out in terms of the ratio of elevation and Bouguer gravity anomaly, the normalized full gradient of a section of the Bouguer gravity anomaly （Gh） and the crustal density structure reveal that （1） the ratio of highs and lows of elevation and Bouguer gravity anomaly is large between Zhengyiguan fault （F4） and Helandonglu fault （F6）, which can be explained due to crustal inhomogeneities related to the uplift of the Qinghai-Tibet block in the northeast; （2） the main active faults correspond to the Gh contour strip or cut the local region, and generally show strong deformation characteristics, for example the Bayanwulashan mountain front fault （F1） or the southeast boundary of Alxa block is in accord with the western change belt of Gh, a belt about 10 km wide that extends to about 30 km; （3） Yinchuan- Pingluo fault （FS） is the seismogenic structure of the Pin- gluo M earthquake, and its focal depth is about 15 km; （4） the Moho depth trend and Bouguer gravity anomaly vari- ation indicates that the regional gravity field is strongly correlated with the Moho discontinuity.展开更多
基金supported by the Key Projects of China Seismic Array(201308011)Earthquake Science(201508006)the China Earthquake Administration,Institute of Seismology Foundation(201326126)
文摘This paper deals with the interpretation of Bouguer gravity anomalies measured along a 250 km long Suhaitu-Etuokeqi gravity profile located at the transitional zone of the Alxa and Ordos blocks where geophysical characteristics are very complex. The analysis is carried out in terms of the ratio of elevation and Bouguer gravity anomaly, the normalized full gradient of a section of the Bouguer gravity anomaly （Gh） and the crustal density structure reveal that （1） the ratio of highs and lows of elevation and Bouguer gravity anomaly is large between Zhengyiguan fault （F4） and Helandonglu fault （F6）, which can be explained due to crustal inhomogeneities related to the uplift of the Qinghai-Tibet block in the northeast; （2） the main active faults correspond to the Gh contour strip or cut the local region, and generally show strong deformation characteristics, for example the Bayanwulashan mountain front fault （F1） or the southeast boundary of Alxa block is in accord with the western change belt of Gh, a belt about 10 km wide that extends to about 30 km; （3） Yinchuan- Pingluo fault （FS） is the seismogenic structure of the Pin- gluo M earthquake, and its focal depth is about 15 km; （4） the Moho depth trend and Bouguer gravity anomaly vari- ation indicates that the regional gravity field is strongly correlated with the Moho discontinuity.
