World Stress Map Conference - International Lithosphere Program ...

More documents

Recommendations

Info

Thursday, October 16 th Poster Session VI: Stress field and interpretation at regional scale Attached or not attached – evidence of crustal stress observations on a weak coupling of the Vrancea slab Birgit Müller and Oliver Heidbach Heidelberg Academy of Sciences and Humanities, Heidelberg, Germany Geophysical Institute, Universität Karlsruhe (TH), Karlsruhe, Germany birgit.mueller@gpi.uni-kalsruhe.de Thies Buchmann CHEVRON, Houston, USA Blanka Sperner Institute of Geology, University of Freiberg, Germany Mihaela Negut PETROM Inc, Romania The crustal stress pattern of Romania provides key insights into whether the Vrancea slab with its seismogenic volume between 70 and 175 km depth is still coupled to the crust and thus acts as a stress guide, or whether it is already in a state of detachment from the crust. Knowledge of the state of the slab under Vrancea is particularly critical because the slab attached to the crust can result in future strong earthquake occurrence in the crust and even in the currently aseismic zone between 40 km and 70 km depth, potentially causing severe damage. Our analysis of the contemporary tectonic stress observations in the context of potential stress sources and the comparison with numerical modelling shows that the crustal stress pattern in Romania is heterogeneous and does not contain long wave-length stress pattern that would be expected if there is a strong present-day coupling between the subducted slab and the upper plate, or if lateral plate boundary forces would control the regional stress pattern. Therefore, we conclude that the crustal stress pattern of Romania is characterized by small differential horizontal stresses where local stress sources (third-order effects) are responsible for the observed heterogeneity of stress orientations and that the subducted slab under Vrancea is only weakly coupled to the crust. 96 3 rd World Stress Map Conference, 15.-17. October 2008 in Potsdam
3 rd World Stress Map Conference, 15.-17. October 2008 in Potsdam Thursday, October 16 th Poster Session VI: Stress field and interpretation at regional scale Stress states based on 3D seismic data from the Dutch subsurface Heijn van Gent and Janos L. Urai Geological Institute, Structural Geology, Tectonics and Geomechanics, RWTH Aachen University h.vangent@ged.rwth-aachen.de Stefan Back and Peter A. Kukla Geological Institute, RWTH Aachen University Klaus Reicherter Neotectonics and Geohazards, RWTH Aachen University To calculate paleostress tensors, information is required on the orientation, and direction of slip of multiple faults. Traditionally, this data is gathered by direct fault plane and slickenside measurement in the field. When a similar method could be applied to seismic data, a potentially massive amount of new strfess data could be extracted, both in space and time. We use high quality, 3D seismic data (courteously provided by the Nederlandse Aardolie Maatschappij, NAM, a Shell operated 50-50 joint venture with ExxonMobile) of the Dutch subsurface to evaluate the potential of 3D seismics for (paleo-)stress reconstruction. In the Groningen gas field, 13 horizons and about 80 major tectonic faults were interpreted in Rotliegend to Tertiary deposits. A detailed study of the shape of horizon cut-offs projected on the fault planes, combined with high-resolution fault interpretation to show undulations, and geometric reconstruction of horizons and faults, was used to estimate the fault slip vectors. This data was then used to calculate the kinematic axes using the Numerical Dynamic Analysis, in order to evaluate the paleostress tensor. In the Groningen area, paleostress tensors were calculated for the Neogene, the Late Paleogene, the Late Cretaceous and a stress state, which most likely represents that of the Early Triassic. All stress states show extension, but the Groningen Block is known not to be inverted during Mesozoic and Cenozoic compressional phases. The calculated paleostress tensors show good correspondence with published paleostress tensors for NW-Europe. The Neogene stress state further corresponds well with the present-day maximum horizontal stresses (SH) as published in the WSM. To validate the workflow, 320 minor, not reactivated faults were interpreted in the brittle Chalk. These were not interpreted in the first phase of this study. Results from this data set show the same Cretaceous stress state as the major faults, with a NE-SW orientated SH. Extending the study to the Dutch offshore Chalk deposits show as a preliminary result that Cretaceous stress here does not correspond to the published regional stress state. This however could represent a local stress state as the study area is located in a zone where three structural trends interact. This study shows there is potential to establish (paleo-)stresses from 3D seismics, where classic paleostress reconstruction is not possible. The scale of the study, compared to the scale of traditional paleostress studies and identification of unambiguous fault slip indicators from seismic data however require further study. 97
Page 3 and 4:
3 rd World Stress Map Conference Fr
Page 5 and 6:
Table of Contents Introduction ....
Page 7 and 8:
Introduction The World Stress Map (
Page 9 and 10:
Invited keynote speakers Nicholas D
Page 11 and 12:
Registration desk The registration
Page 13 and 14:
Friday, October 17 th - Reception i
Page 15 and 16:
Saturday 18. October - Field trip t
Page 17 and 18:
3 rd World Stress Map Conference, 1
Page 19 and 20:
Poster Presentations - Wednesday, O
Page 21 and 22:
Poster Presentations - Thursday, Oc
Page 23 and 24:
Page 25 and 26:
Wednesday, October 15 th Oral Sessi
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Wednesday, October 15 th Poster Ses
Page 45 and 46:
Page 47 and 48:
Page 49 and 50: Wednesday, October 15 th Poster Ses
Page 51 and 52: 3 rd World Stress Map Conference, 1
Page 67 and 68: Thursday, October 16 th Oral Sessio
Page 81 and 82: Thursday, October 16 th Poster Sess
Page 99: 3 rd World Stress Map Conference, 1
Page 115 and 116: List of participants Altmann, Johan
Page 117 and 118: Content of the CD-ROM The attached
show all

World Stress Map Conference - International Lithosphere Program ...

Create successful ePaper yourself

Delete template?

Save as template?