GeoexplorationPub Date : 1989-07-01DOI: 10.1016/0016-7142(89)90038-0
Jonas Lindgren, Trine Dahl-Jensen
{"title":"Reflection seismic investigation of the Dalasandstone area, Central Sweden","authors":"Jonas Lindgren, Trine Dahl-Jensen","doi":"10.1016/0016-7142(89)90038-0","DOIUrl":"10.1016/0016-7142(89)90038-0","url":null,"abstract":"","PeriodicalId":100579,"journal":{"name":"Geoexploration","volume":"26 1","pages":"Page 60"},"PeriodicalIF":0.0,"publicationDate":"1989-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0016-7142(89)90038-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77245660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
GeoexplorationPub Date : 1989-07-01DOI: 10.1016/0016-7142(89)90028-8
Dan Dyrelius
{"title":"Simultaneous interpretation of surface and borehole gravity data from the Siljan area","authors":"Dan Dyrelius","doi":"10.1016/0016-7142(89)90028-8","DOIUrl":"10.1016/0016-7142(89)90028-8","url":null,"abstract":"","PeriodicalId":100579,"journal":{"name":"Geoexploration","volume":"26 1","pages":"Page 53"},"PeriodicalIF":0.0,"publicationDate":"1989-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0016-7142(89)90028-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"96746469","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
GeoexplorationPub Date : 1989-07-01DOI: 10.1016/0016-7142(89)90052-5
Hans Palm
{"title":"Regional seismic reflection profiling in the caledonides: Data acquisition and preliminary results","authors":"Hans Palm","doi":"10.1016/0016-7142(89)90052-5","DOIUrl":"https://doi.org/10.1016/0016-7142(89)90052-5","url":null,"abstract":"","PeriodicalId":100579,"journal":{"name":"Geoexploration","volume":"26 1","pages":"Pages 70-71"},"PeriodicalIF":0.0,"publicationDate":"1989-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0016-7142(89)90052-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92138617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
GeoexplorationPub Date : 1989-07-01DOI: 10.1016/0016-7142(89)90017-3
Joāo B.C Silva, Alterêdo O Cutrim
{"title":"A robust maximum likelihood method for gravity and magnetic interpretation","authors":"Joāo B.C Silva, Alterêdo O Cutrim","doi":"10.1016/0016-7142(89)90017-3","DOIUrl":"10.1016/0016-7142(89)90017-3","url":null,"abstract":"<div><p>Historically, automatic curve-matching algorithms have employed the least squares method which minimizes the <em>L</em><sub>2</sub> norm of the residuals. The least squares method, however, is very sensitive to the presence of outliers in data, and the alternative robust method employed so far has been the minimum absolute errors which minimizes the <em>L</em><sub>1</sub> norm of the residuals.</p><p>Associating the type of residual norm being minimized with the sensitivity of the interpretation method to the presence of outliers may lead, however, to the false impression that there is no method more robust than the minimization of the <em>L</em><sub>1</sub> norm.</p><p>Another viewpoint is to associate robustness with the probability density function describing the errors. Long-tailed distributions are related to more robust methods. Both least squares and minimum absolute errors may be derived from a maximum likelihood approach assuming that the errors present in the data follow a Gaussian or Laplace distribution, respectively. In this paper we present a maximum likelihood estimator based on the assumptions of errors following a Cauchy distribution which is more long-tailed than either the Gaussian or the Laplace distribution. As a result, the derived method is more robust than either the least squares or the minimum absolute errors.</p><p>The superior performance of the method as compared with the least squares method in the presence of Gaussian and geological noise is demonstrated using synthetic and field data. The results show that the method is less sensitive to the initial guess than the least squares. It produces better and more consistent solutions which are, therefore, less ambiguous. Also, as the method takes into account the presence of geological noise, it may be used to obtain a rough, but reliable outline of the sources, using simple interpretation models. This feature might be useful in designing automatic interpretation algorithms.</p></div>","PeriodicalId":100579,"journal":{"name":"Geoexploration","volume":"26 1","pages":"Pages 1-31"},"PeriodicalIF":0.0,"publicationDate":"1989-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0016-7142(89)90017-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78583852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
GeoexplorationPub Date : 1989-07-01DOI: 10.1016/0016-7142(89)90023-9
Bo Löfroth
{"title":"Ground probing radar measurements for water exploration: A case study","authors":"Bo Löfroth","doi":"10.1016/0016-7142(89)90023-9","DOIUrl":"10.1016/0016-7142(89)90023-9","url":null,"abstract":"","PeriodicalId":100579,"journal":{"name":"Geoexploration","volume":"26 1","pages":"Pages 49-50"},"PeriodicalIF":0.0,"publicationDate":"1989-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0016-7142(89)90023-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77431357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
GeoexplorationPub Date : 1989-07-01DOI: 10.1016/0016-7142(89)90039-2
P. Zhang, L.B. Pedersen, T.M. Rasmussen
{"title":"Near surface distortion of electrical field in the Siljan impact area","authors":"P. Zhang, L.B. Pedersen, T.M. Rasmussen","doi":"10.1016/0016-7142(89)90039-2","DOIUrl":"10.1016/0016-7142(89)90039-2","url":null,"abstract":"","PeriodicalId":100579,"journal":{"name":"Geoexploration","volume":"26 1","pages":"Pages 60-61"},"PeriodicalIF":0.0,"publicationDate":"1989-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0016-7142(89)90039-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74106046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
GeoexplorationPub Date : 1989-07-01DOI: 10.1016/0016-7142(89)90048-3
Mark-Enar Hansson
{"title":"Kiirunavaara: A comment on the low-magnetic areas on both sides of the orebody and calculations of probable depths of the ore. Principle of the oreforming process","authors":"Mark-Enar Hansson","doi":"10.1016/0016-7142(89)90048-3","DOIUrl":"10.1016/0016-7142(89)90048-3","url":null,"abstract":"","PeriodicalId":100579,"journal":{"name":"Geoexploration","volume":"26 1","pages":"Pages 67-68"},"PeriodicalIF":0.0,"publicationDate":"1989-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0016-7142(89)90048-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85680744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
GeoexplorationPub Date : 1989-07-01DOI: 10.1016/0016-7142(89)90018-5
Maurice K Seguin, Janusz Frydecki
{"title":"Densités et anomalies gravimétriques de l'intrusif du mont mégantic","authors":"Maurice K Seguin, Janusz Frydecki","doi":"10.1016/0016-7142(89)90018-5","DOIUrl":"10.1016/0016-7142(89)90018-5","url":null,"abstract":"<div><p>An accurate estimate of the Bouguer density is needed to make corrections of the gravity data and to interpret the results. Many methods have been used for this purpose. Amongst these, the following can be mentioned: field sampling and laboratory measurements, geophysical logs, data relative to seismic velocities and gravity data. Surface sampling and the relation density-seismic velocity are affected by surficial alteration of the rock units. This is why an indirect determination with the help of gravimetry is often more representative. However, the relation Bouguer anomaly versus altitude for estimate of density is lacking precision. A more rigorous method related to the free air anomaly is proposed. This density determination method is applied to the Mount Megantic area, an intrusive of Cretaceous age belonging to the Monteregian Group. The mean density for the whole of the area investigated is 2647 kg m<sup>−3</sup>. The density of each geological formation was estimated individually. The results obtained show that the calibration: free air anomaly versus altitude is the most reliable.</p></div>","PeriodicalId":100579,"journal":{"name":"Geoexploration","volume":"26 1","pages":"Pages 33-46"},"PeriodicalIF":0.0,"publicationDate":"1989-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0016-7142(89)90018-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78324705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}