TY - JOUR
T1 - Kinematics of Active Deformation in the Malawi Rift and Rungwe Volcanic Province, Africa
AU - Ebinger, C. J.
AU - Oliva, Sarah Jaye
AU - Pham, Thi Quan
AU - Peterson, Katherine
AU - Chindandali, Patrick
AU - Illsley-Kemp, Finnigan
AU - Drooff, Connor
AU - Shillington, Donna J.
AU - Accardo, Natalie J.
AU - Gallacher, Ryan J.
AU - Gaherty, J.
AU - Nyblade, Andrew A.
AU - Mulibo, Gabriel
N1 - Funding Information:
We thank Olaf Zielke and an anonymous reviewer for constructive comments on the manuscript. We are grateful for the assistance of many during the siting and acquisition of the passive earthquake monitoring, with special thanks to Gabriel Mbogoni, Marsella Kachingwe, Godson Kamihanda, Gabrielle Tepp, John Paul O'Donnell. Shelby Corning helped build the earthquake catalogue. C. E. acknowledges support of National Science Foundation grant 1734884. F. I. K. is funded through the New Zealand Ministry of Business, Innovation, and Employment funded ECLIPSE program. All seismic waveform data are archived at IRIS (SEGMeNT doi:10.7914/SN/YQ_2013), and the earthquake catalogue has been provided to the International Seismological Centre for open access. The absolute earthquake catalogue is also available for download with the supporting information.
Publisher Copyright:
©2019. American Geophysical Union. All Rights Reserved.
PY - 2019/8/1
Y1 - 2019/8/1
N2 - Although the deep, wide basins of the Western rift, Africa, have served as analogues for the evolution of half-graben basins, the geometry and kinematics of the border, intrabasinal, and transfer fault systems have been weakly constrained. Despite the >100-km-long fault systems bounding basins, little was known of seismicity patterns or the potential for M > 7.5 earthquakes. Using our new local earthquake database from the 2013-2015 Study of Extension and maGmatism in Malawi aNd Tanzania (SEGMeNT) seismic array (57 onshore, 32 lake-bottom stations) and TANGA14 (13 stations), we examine the kinematics and extension direction of the Rungwe Volcanic Province and northern Malawi rift. We relocated earthquakes using a new 1-D velocity model and both absolute and double-difference relocation methods. Local magnitudes of 1,178 earthquakes within the array are 0.7 < ML < 5.2 with a b-value 0.77 ± 0.03, and magnitude of completeness ML 1.9. Focal mechanism solutions for 63 earthquakes reveal predominantly normal and oblique-slip motion, and full moment tensor solutions for ML 4.5, 5.2 earthquakes have centroid depths within 2 km of catalog depths. The preferred nodal planes dip more than 40° from surface to >25-km depths. Extension direction from local earthquakes and source mechanisms of teleseismically detected earthquakes are approximately N58°E and N65°E, respectively, refuting earlier interpretations of a NW-SE transform fault system. The low b-value indicating strong coupling across crustal-scale border faults, border fault lengths >100 km, and evidence for aseismic deformation together indicate that infrequent M > 7.5 earthquakes are possible within this cratonic rift system.
AB - Although the deep, wide basins of the Western rift, Africa, have served as analogues for the evolution of half-graben basins, the geometry and kinematics of the border, intrabasinal, and transfer fault systems have been weakly constrained. Despite the >100-km-long fault systems bounding basins, little was known of seismicity patterns or the potential for M > 7.5 earthquakes. Using our new local earthquake database from the 2013-2015 Study of Extension and maGmatism in Malawi aNd Tanzania (SEGMeNT) seismic array (57 onshore, 32 lake-bottom stations) and TANGA14 (13 stations), we examine the kinematics and extension direction of the Rungwe Volcanic Province and northern Malawi rift. We relocated earthquakes using a new 1-D velocity model and both absolute and double-difference relocation methods. Local magnitudes of 1,178 earthquakes within the array are 0.7 < ML < 5.2 with a b-value 0.77 ± 0.03, and magnitude of completeness ML 1.9. Focal mechanism solutions for 63 earthquakes reveal predominantly normal and oblique-slip motion, and full moment tensor solutions for ML 4.5, 5.2 earthquakes have centroid depths within 2 km of catalog depths. The preferred nodal planes dip more than 40° from surface to >25-km depths. Extension direction from local earthquakes and source mechanisms of teleseismically detected earthquakes are approximately N58°E and N65°E, respectively, refuting earlier interpretations of a NW-SE transform fault system. The low b-value indicating strong coupling across crustal-scale border faults, border fault lengths >100 km, and evidence for aseismic deformation together indicate that infrequent M > 7.5 earthquakes are possible within this cratonic rift system.
UR - http://www.scopus.com/inward/record.url?scp=85070690505&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85070690505&partnerID=8YFLogxK
U2 - 10.1029/2019GC008354
DO - 10.1029/2019GC008354
M3 - Article
AN - SCOPUS:85070690505
SN - 1525-2027
VL - 20
SP - 3928
EP - 3951
JO - Geochemistry, Geophysics, Geosystems
JF - Geochemistry, Geophysics, Geosystems
IS - 8
ER -