物探与化探
物探與化探
물탐여화탐
GEOPHYSICAL AND GEOCHEMICAL EXPLORATION
2015年
1期
1-11
,共11页
169 km以远%地壳质量%重力校正值%高精度计算%数值特征
169 km以遠%地殼質量%重力校正值%高精度計算%數值特徵
169 km이원%지각질량%중력교정치%고정도계산%수치특정
distance over 169 km%mass of the Earth's crust%gravity emendation value%high precision computation%numerical char-acteristics
以前国内重力勘探教科书中，关于2．0 km以远地壳质量重力校正值的计算仅限于2．0～166．7 km圆形环带以内，并且采用的是直角坐标系内成立的计算公式。近年，中国地质调查局推出直角坐标系公式和球坐标系公式一起应用的重力校正值计算程序，但校正值计算涉及范围仍然局限于2．0～166．7 km圆形环带内。笔者曾推导出球壳型六面体重力场△g（ zi ）公式和其他与重力校正计算相关的公式，现用这些公式开展纯球坐标系内地壳质量的重力校正值高精度计算及其数值特征研究。取得的成果是：①全球陆地和海洋表面、尺度约40 km正方形网格上，169 km以远地壳全部质量重力校正值计算；②中国陆地2′×2′网格上，169 km以远地壳全部质量重力校正值计算；③西藏雅江大转弯3°×2°小区地表、尺度约0．556 km正方形网格上，169 km以远地壳全部质量重力校正值计算。通过对上述全球和局部地区169 km以远地壳质量的重力校正值分布特征分析，得到如下结论：①全球重力校正值的最大值、最小值和平均值分别为106．990×10－5 m／s2（87．877°E，32．271°N），－41．146×10－5 m／s2（166．122°E，28．327°N）和－16．439×10－5 m／s2，其数值分布特征与全球高程／海深分布特征基本一致。②在局部地区，169～1272 km大环带的地壳质量的陆地地形校正值分布特征与该区高程分布特征基本一致。这说明，在地形高程差异大的地区，重力校正值中存在与地形高程正相关的高频成分，与以前众多专家的认识大不相同。实际上，该高频成分是由计算区本身相邻计算点之间存在较大的高程差值引起的。③无论局部地区及其周围陆高或海深变化多么大，1272 km以远地壳质量的重力校正值均近似为数值很小的常数，可以不计算。④当局部地区及其周围高程或海深变化均很平缓时，169 km以远地壳全部质量的重力校正值也近似为常数，也可以不计算。此成果对于完善地壳质量重力校正值高精度计算有重要意义。
以前國內重力勘探教科書中，關于2．0 km以遠地殼質量重力校正值的計算僅限于2．0～166．7 km圓形環帶以內，併且採用的是直角坐標繫內成立的計算公式。近年，中國地質調查跼推齣直角坐標繫公式和毬坐標繫公式一起應用的重力校正值計算程序，但校正值計算涉及範圍仍然跼限于2．0～166．7 km圓形環帶內。筆者曾推導齣毬殼型六麵體重力場△g（ zi ）公式和其他與重力校正計算相關的公式，現用這些公式開展純毬坐標繫內地殼質量的重力校正值高精度計算及其數值特徵研究。取得的成果是：①全毬陸地和海洋錶麵、呎度約40 km正方形網格上，169 km以遠地殼全部質量重力校正值計算；②中國陸地2′×2′網格上，169 km以遠地殼全部質量重力校正值計算；③西藏雅江大轉彎3°×2°小區地錶、呎度約0．556 km正方形網格上，169 km以遠地殼全部質量重力校正值計算。通過對上述全毬和跼部地區169 km以遠地殼質量的重力校正值分佈特徵分析，得到如下結論：①全毬重力校正值的最大值、最小值和平均值分彆為106．990×10－5 m／s2（87．877°E，32．271°N），－41．146×10－5 m／s2（166．122°E，28．327°N）和－16．439×10－5 m／s2，其數值分佈特徵與全毬高程／海深分佈特徵基本一緻。②在跼部地區，169～1272 km大環帶的地殼質量的陸地地形校正值分佈特徵與該區高程分佈特徵基本一緻。這說明，在地形高程差異大的地區，重力校正值中存在與地形高程正相關的高頻成分，與以前衆多專傢的認識大不相同。實際上，該高頻成分是由計算區本身相鄰計算點之間存在較大的高程差值引起的。③無論跼部地區及其週圍陸高或海深變化多麽大，1272 km以遠地殼質量的重力校正值均近似為數值很小的常數，可以不計算。④噹跼部地區及其週圍高程或海深變化均很平緩時，169 km以遠地殼全部質量的重力校正值也近似為常數，也可以不計算。此成果對于完善地殼質量重力校正值高精度計算有重要意義。
이전국내중력감탐교과서중，관우2．0 km이원지각질량중력교정치적계산부한우2．0～166．7 km원형배대이내，병차채용적시직각좌표계내성립적계산공식。근년，중국지질조사국추출직각좌표계공식화구좌표계공식일기응용적중력교정치계산정서，단교정치계산섭급범위잉연국한우2．0～166．7 km원형배대내。필자증추도출구각형륙면체중력장△g（ zi ）공식화기타여중력교정계산상관적공식，현용저사공식개전순구좌표계내지각질량적중력교정치고정도계산급기수치특정연구。취득적성과시：①전구륙지화해양표면、척도약40 km정방형망격상，169 km이원지각전부질량중력교정치계산；②중국륙지2′×2′망격상，169 km이원지각전부질량중력교정치계산；③서장아강대전만3°×2°소구지표、척도약0．556 km정방형망격상，169 km이원지각전부질량중력교정치계산。통과대상술전구화국부지구169 km이원지각질량적중력교정치분포특정분석，득도여하결론：①전구중력교정치적최대치、최소치화평균치분별위106．990×10－5 m／s2（87．877°E，32．271°N），－41．146×10－5 m／s2（166．122°E，28．327°N）화－16．439×10－5 m／s2，기수치분포특정여전구고정／해심분포특정기본일치。②재국부지구，169～1272 km대배대적지각질량적륙지지형교정치분포특정여해구고정분포특정기본일치。저설명，재지형고정차이대적지구，중력교정치중존재여지형고정정상관적고빈성분，여이전음다전가적인식대불상동。실제상，해고빈성분시유계산구본신상린계산점지간존재교대적고정차치인기적。③무론국부지구급기주위륙고혹해심변화다요대，1272 km이원지각질량적중력교정치균근사위수치흔소적상수，가이불계산。④당국부지구급기주위고정혹해심변화균흔평완시，169 km이원지각전부질량적중력교정치야근사위상수，야가이불계산。차성과대우완선지각질량중력교정치고정도계산유중요의의。
In the previous textbooks of gravitational prospecting, the computation of gravity emendation values arising from mass of the Earth's crust at the distance over 2 km from the observation point is confined only to an area of circular ring 2.0~166.7 km in breadth and the computation expressions coming into existence in the orthogonal coordinate system are adopted. China Geological Survey has generalized in recent years the computation program of gravity emendation value that adopts the computation expressions both in the or?thogonal coordinate system and in the spherical coordinate system;nevertheless, the computation of gravity emendation values remains confined to an area of circular ring 2.0~166.7 km in breadth and fails to take into account the gravitation arising from mass of the Earth's crust at the distance over 166.7 km from the observation point. 10 years ago, the authors deduced alone gravity expression of the hexahedron with a spherical crust form and other expressions re?lated to the computation of gravity emendation values. After this, adopting these expressions, the authors conducted researches on high precision computation and numerical value characteristics of gravity emendation values arising from mass of the Earth's crust in pure spherical coordinate system, with the following computation achievements obtained: ① high precision computation result of "Gravity Emendation Value arising from Mass of the Earth's Crust at Distance Over 169 km From Observation Point" ( GEVMECDO 169 km FOP ) at the square grid 40 km in breadth on whole Earth's land and ocean surface; ② high precision computation achievements of GEVMECDO 169 km FOP at longitude and latitude grid of China's continent;③ high precision computation achievements of GEVM?ECDO 169km FOP at the square grid 0.556km in breadth in local 3°×2° area along the large curved portion of the Yarlung Zang Zang?bo River. Based on analyzing numerical values distribution characteristics of GEVMECDO 169 km FOP on the whole Earth's and local sur?faces, the authors have arrived at the following conclusions d:①The maximum, minimum and mean values of gravity emendation val?ues on the whole Earth's surface are 106.990 mgal (87.877°E, 32.271°N), -41.146 mgal (166.122°E,28.327°N) and -16.439 mGal respectively;the distribution characteristics of these values are in the main consistent with the distribution characteristics of the Earth's land altitude/sea depth values. ② The distribution characteristics of gravity terrain emendation values in a local area arising from mass of the Earth's crust in large circular rings 169-1 272 km in breadth are in the main consistent with the distribution character?istics of land altitude values in this local area. These data suggest that there are high frequency components in gravity emendation values of the area with larger altitude differences,and these high frequency components with terrain altitude values have positive correlation. These facts differ remarkably from the opinions put forward by many researchers. In fact, these high frequency components result from larger altitude differences of neighboring points in a local area. ③No mater how large the differences of altitudes /sea depths in a local area and its peripheries are, these GEVMCDO 1 272 km FOP are approximately close to a very small constant and may not be compu?ted;④ Where the altitude or sea depth of local area and its peripheries changes smoothly, the gravity emendation values of the whole mass of the crust over the distance of 169km are approximately close to a constant and hence may not be calculated. The results achieved by the authors have important significance for perfecting high precision computation of gravity emendation val?ues arising from mass of the Earth's crust. The authors suggest introducing these achievements into new textbooks of gravitational pros?pecting and also propose to study and extend this research topic with high precision and high speed with the purpose of convenient ap?plication of gravity emendation values arising from mass of the Earth's crust on the basis of these achievements.
