Evidence for cross rift structural controls on deformation and seismicity at a continental rift caldera

Abstract In continental rifts structural heterogeneities, such as pre-existing faults and foliations, are thought to influence shallow crustal processes, particularly the formation of rift faults, magma reservoirs and surface volcanism. We focus on the Corbetti caldera, in the southern central Main Ethiopian Rift. We measure the surface deformation between 22nd June 2007 and 25th March 2009 using ALOS and ENVISAT SAR interferograms and observe a semi-circular pattern of deformation bounded by a sharp linear feature cross-cutting the caldera, coincident with the caldera long axis. The signal reverses in sign but is not seasonal: from June to December 2007 the region south of this structure moves upwards 3 cm relative to the north, while from December 2007 until November 2008 it subsides by 2 cm. Comparison of data taken from two different satellite look directions show that the displacement is primarily vertical. We discuss potential mechanisms and conclude that this deformation is associated with pressure changes within a shallow ( Analysis of the distribution of post-caldera vents and cones inside the caldera shows their locations are statistically consistent with this fault structure, indicating that the fault has also controlled the migration of magma from a reservoir to the surface over tens of thousands of years. Spatial patterns of seismicity are consistent with a cross-rift structure that extents outside the caldera and to a depth of ∼30 km, and patterns of seismic anisotropy suggests stress partitioning occurs across the structure. We discuss the possible nature of this structure, and conclude that it is most likely associated with the Goba–Bonga lineament, which cross-cuts and pre-dates the current rift. Our observations show that pre-rift structures play an important role in magma transport and shallow hydrothermal processes, and therefore they should not be neglected when discussing these processes.

[1]  G. Williams-Jones,et al.  Microgravity changes at the Laguna del Maule volcanic field: Magma‐induced stress changes facilitate mass addition , 2017 .

[2]  M. Simons,et al.  An InSAR‐based survey of volcanic deformation in the southern Andes , 2004 .

[3]  R. W. England,et al.  Northern Main Ethiopian Rift crustal structure from new high-precision gravity data , 2006, Geological Society, London, Special Publications.

[4]  Gianfranco Fornaro,et al.  A new algorithm for surface deformation monitoring based on small baseline differential SAR interferograms , 2002, IEEE Trans. Geosci. Remote. Sens..

[5]  Marie-Pierre Doin,et al.  Corrections of stratified tropospheric delays in SAR interferometry: Validation with global atmospheric models , 2009 .

[6]  S. Hautot,et al.  Lower crustal earthquakes near the Ethiopian rift induced by magmatic processes , 2009 .

[7]  R. Bendick,et al.  Monsoonal loading in Ethiopia and Eritrea from vertical GPS displacement time series , 2015 .

[8]  C. Ebinger,et al.  Upper-mantle seismic structure in a region of incipient continental breakup: northern Ethiopian rift , 2005 .

[9]  C. Werner,et al.  GAMMA SAR AND INTERFEROMETRIC PROCESSING SOFTWARE , 2000 .

[10]  Claude Rangin,et al.  THE NORTH ANATOLIAN FAULT: A NEW LOOK , 2005 .

[11]  Rowena B. Lohman,et al.  Constraints on surface deformation in the Seattle, WA, urban corridor from satellite radar interferometry time-series analysis , 2008 .

[12]  J. Gottsmann,et al.  Faults and ground uplift at active calderas , 2006, Geological Society, London, Special Publications.

[13]  G. Corti,et al.  Evolution, distribution, and characteristics of rifting in southern Ethiopia , 2014 .

[14]  A. Melkonian,et al.  Volcanic hotspots of the central and southern Andes as seen from space by ASTER and MODVOLC between the years 2000 and 2010 , 2013 .

[15]  E. Fielding,et al.  Predictability of hydraulic head changes and characterization of aquifer‐system and fault properties from InSAR‐derived ground deformation , 2014 .

[16]  Zhong Lu,et al.  Magmatic activity beneath the quiescent Three Sisters volcanic center, central Oregon Cascade Range, USA , 2002 .

[17]  J. Chorowicz,et al.  Volcanic vents rooted on extension fractures and their geodynamic implications in the Ethiopian Rift , 1997 .

[18]  J. Cole,et al.  Calderas and caldera structures: a review , 2005 .

[19]  F. Salvini,et al.  Elliptic calderas in the Ethiopian Rift: control of pre-existing structures , 2003 .

[20]  F. Amelung,et al.  A new model for the growth of basaltic shields based on deformation of Fernandina volcano, Galápagos Islands , 2013 .

[21]  K. Feigl,et al.  Radar interferometry and its application to changes in the Earth's surface , 1998 .

[22]  P. Lipman,et al.  Subsidence of ash-flow calderas: relation to caldera size and magma-chamber geometry , 1997 .

[23]  G. Leonard,et al.  Volcanic and structural evolution of the Okataina Volcanic Centre; dominantly silicic volcanism associated with the Taupo Rift, New Zealand , 2010 .

[24]  G. Corti,et al.  Evolution of the Main Ethiopian Rift in the frame of Afar and Kenya rifts propagation , 2005 .

[25]  J. Wookey,et al.  Seismicity associated with magmatism, faulting and hydrothermal circulation at Aluto Volcano, Main Ethiopian Rift , 2017 .

[26]  K. Feigl,et al.  Discrimination of geophysical phenomena in satellite radar interferograms , 1995 .

[27]  G. R. Keller,et al.  Crustal structure of the northern Main Ethiopian Rift from the EAGLE controlled-source survey; a snapshot of incipient lithospheric break-up , 2006, Geological Society, London, Special Publications.

[28]  T. Korme,et al.  The Role of Pre-existing Structures in the Origin, Propagation and Architecture of Faults in the Main Ethiopian Rift , 2004 .

[29]  C. W. Chen,et al.  Two-dimensional phase unwrapping with use of statistical models for cost functions in nonlinear optimization. , 2001, Journal of the Optical Society of America. A, Optics, image science, and vision.

[30]  J. Biggs,et al.  Influence of regional tectonics and pre-existing structures on the formation of elliptical calderas in the Kenyan Rift , 2015, Special Publications.

[31]  S. Saunders.  The shallow plumbing system of Rabaul caldera: a partially intruded ring fault? , 2001 .

[32]  Riccardo Lanari,et al.  Satellite radar interferometry time series analysis of surface deformation for Los Angeles, California , 2004 .

[33]  S. Hall,et al.  The effect of microstructure and nonlinear stress on anisotropic seismic velocities , 2008 .

[34]  Tamsin A. Mather,et al.  Applicability of InSAR to tropical volcanoes: insights from Central America , 2013 .

[35]  T. Wright,et al.  Toward mapping surface deformation in three dimensions using InSAR , 2004 .

[36]  Z. Shipton,et al.  Elliptical calderas in active tectonic settings: an experimental approach , 2005 .

[37]  C. Jaupart,et al.  The impact of a volcanic edifice on intrusive and eruptive activity , 2014 .

[38]  G. Wadge,et al.  Historical Volcanism and the State of Stress in the East African Rift System , 2016, Front. Earth Sci..

[39]  J. Gottsmann,et al.  The large‐scale surface uplift in the Altiplano‐Puna region of Bolivia: A parametric study of source characteristics and crustal rheology using finite element analysis , 2013 .

[40]  B. Taisne,et al.  Effect of solidification on a propagating dike. , 2011 .

[41]  Richard Gloaguen,et al.  Three-dimensional seismic imaging of a protoridge axis in the Main Ethiopian rift , 2004 .

[42]  Ian Parsons,et al.  Surface deformation due to shear and tensile faults in a half-space , 1986 .

[43]  G. Chiodini,et al.  Causes of unrest at silicic calderas in the East African Rift: New constraints from InSAR and soil‐gas chemistry at Aluto volcano, Ethiopia , 2016 .

[44]  R. Mcconnell.  Geological Development of the Rift System of Eastern Africa , 1972 .

[45]  C. Ebinger,et al.  Crustal tomographic imaging of a transitional continental rift: The Ethiopian rift , 2008 .

[46]  I. Isola,et al.  The intimate relationship between strain and magmatism: A numerical treatment of clustered monogenetic fields in the Main Ethiopian Rift , 2013 .

[47]  E. Rivalta,et al.  Off-rift volcanism in rift zones determined by crustal unloading , 2014 .

[48]  J. Gottsmann,et al.  Magma storage in a strike-slip caldera , 2016, Nature Communications.

[49]  J. Rowland,et al.  Spatial distribution and alignments of volcanic centers: Clues to the formation of monogenetic volcanic fields , 2013 .

[50]  C. Doglioni,et al.  Left-lateral transtension along the Ethiopian Rift and constrains on the mantle-reference plate motions , 2014 .

[51]  T. Farr,et al.  Shuttle radar topography mission produces a wealth of data , 2000 .

[52]  Claudia Troise,et al.  Evidence for fluid migration as the source of deformation at Campi Flegrei caldera (Italy) , 2006 .

[53]  C. Werner,et al.  Radar interferogram filtering for geophysical applications , 1998 .

[54]  Marco Bonini,et al.  Quaternary oblique extensional tectonics in the Ethiopian Rift (Horn of Africa) , 1998 .

[55]  K. Verner,et al.  Wendo Koshe Pumice: The latest Holocene silicic explosive eruption product of the Corbetti Volcanic System (Southern Ethiopia) , 2016 .

[56]  Joan Martí,et al.  The Las Cañadas caldera (Tenerife, Canary Islands): an overlapping collapse caldera generated by magma-chamber migration , 2000 .

[57]  M. Bonafede,et al.  Hot fluid migration: an efficient source of ground deformation: application to the 1982–1985 crisis at Campi Flegrei-Italy , 1991 .

[58]  Virginie Pinel,et al.  Magma chamber behavior beneath a volcanic edifice , 2003 .

[59]  D. S. Stamps,et al.  A kinematic model for the East African Rift , 2008 .

[60]  B. D. Vries,et al.  The Managua Graben and Las Sierras-Masaya volcanic complex (Nicaragua); pull-apart localization by an intrusive complex: results from analogue modeling , 2005 .

[61]  G. Woldegabriel,et al.  Geology, geochronology, and rift basin development in the central sector of the Main Ethiopia Rift , 1990 .

[62]  Frank H. Webb,et al.  Neutral atmospheric delay in interferometric synthetic aperture radar applications: Statistical description and mitigation , 2003 .

[63]  Gian Franco Sacco,et al.  InSAR Scientific Computing Environment , 2011 .

[64]  Juliet Biggs,et al.  Multiple inflation and deflation events at Kenyan volcanoes, East African Rift , 2009 .

[65]  S. Kattenhorn,et al.  Varying styles of magmatic strain accommodation across the East African Rift , 2015 .

[66]  J. Wookey,et al.  A strategy for automated analysis of passive microseismic data to image seismic anisotropy and fracture characteristics , 2010 .

[67]  Wenbin Xu,et al.  The 2007–8 volcanic eruption on Jebel at Tair island (Red Sea) observed by satellite radar and optical images , 2012, Bulletin of Volcanology.

[68]  C. Ebinger,et al.  Continental breakup in magmatic provinces: An Ethiopian example , 2001 .

[69]  G. Corti,et al.  Continental rift evolution: From rift initiation to incipient break-up in the Main Ethiopian Rift, East Africa , 2009 .

[70]  R. Mcconnell,et al.  East African Rift System , 1969, Nature.

[71]  James P. Verdon,et al.  Imaging fractures and sedimentary fabrics using shear wave splitting measurements made on passive seismic data , 2009 .

[72]  Richard H. Sibson,et al.  Structural controls on hydrothermal flow in a segmented rift system, Taupo Volcanic Zone, New Zealand , 2004 .

[73]  Zygmunt L. Szpak,et al.  Guaranteed Ellipse Fitting with a Confidence Region and an Uncertainty Measure for Centre, Axes, and Orientation , 2015, Journal of Mathematical Imaging and Vision.

[74]  A. Peccerillo,et al.  Relationships between mafic and peralkaline silicic magmatism in continental rift settings: A petrological, geochemical and isotopic study of the Gedemsa volcano, Central Ethiopian rift , 2003 .

[75]  Jean Virieux,et al.  Probabilistic Earthquake Location in 3D and Layered Models , 2000 .

[76]  V. Troll,et al.  Formation of caldera periphery faults: an experimental study , 2001 .

[77]  P. Mohr.  Transcurrent Faulting in the Ethiopian Rift System , 1968, Nature.

[78]  J. Biggs,et al.  The lateral extent of volcanic interactions during unrest and eruption , 2016 .

[79]  A. Tsonis,et al.  The Pacific decadal oscillation and long‐term climate prediction , 2000 .

[80]  K. Keranen,et al.  Discontinuous and diachronous evolution of the Main Ethiopian Rift: Implications for development of continental rifts , 2008 .

[81]  G. Corti,et al.  Fault architecture in the Main Ethiopian Rift and comparison with experimental models: Implications for rift evolution and Nubia–Somalia kinematics , 2011 .

[82]  V. Acocella.  Understanding caldera structure and development: An overview of analogue models compared to natural calderas , 2007 .