@article{fdi:010062241,
  title = {{T}he {A}l {H}oceima {M}w 6.4 earthquake of 24 {F}ebruary 2004 and its aftershocks sequence},
  author = {van der {W}oerd, {J}. and {D}orbath, {C}atherine and {O}usadou, {F}. and {D}orbath, {L}ouis and {D}elouis, {B}. and {J}acques, {E}. and {T}apponnier, {P}. and {H}ahou, {Y}. and {M}enzhi, {M}. and {F}rogneux, {M}. and {H}aessler, {H}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he {A}l {H}oceima {M}w 6.4 earthquake of 24 {F}ebruary 2004 that occurred in the eastern {R}if region of {M}orocco already hit by a large event in {M}ay 1994 ({M}w 5.9) has been followed by numerous aftershocks in the months following the event. {T}he aftershock sequence has been monitored by a temporary network of 17 autonomous seismic stations during 15 days (28 {M}arch-10 {A}pril) in addition to 5 permanent stations of the {M}oroccan seismic network ({CNRST}, {SPG}, {R}abat). {T}his network allowed locating accurately about 650 aftershocks that are aligned in two directions, about {N}10-20{E} and {N}110-120{E}, in rough agreement with the two nodal planes of the focal mechanism ({H}arvard). {T}he aftershock alignments are long enough, about 20 km or more, to correspond both to the main rupture plane. {T}o further constrain the source of the earthquake main shock and aftershocks (mb > 3.5) have been relocated thanks to regional seismic data from {M}orocco and {S}pain. {W}hile the main shock is located at the intersection of the aftershock clouds, most of the aftershocks are aligned along the {N}10-20{E} direction. {T}his direction together with normal sinistral slip implied by the focal mechanism is similar with the direction and mechanisms of active faults in the region, particularly the {N}10{E} {T}rougout oblique normal fault. {I}ndeed, the {A}l {H}oceima region is dominated by an approximate {ENE}-{SSW} direction of extension, with oblique normal faults. {T}hree major 10-30 km-long faults, oriented {NNE}-{SSW} to {NW}-{SE} are particularly clear in the morphology, the {A}jdir and {T}rougout faults, west and east of the {A}l {H}oceima basin, respectively, and the {NS} {R}ouadi fault 20 km to the west. {T}hese faults show clear evidence of recent vertical displacements during the late {Q}uaternary such as uplifted alluvial terraces along {O}ued {R}ihs, offset fan surfaces by the {R}ouadi fault and also uplifted and tilted abandoned marine terraces on both sides of the {A}l {H}oceima bay. {H}owever, the {N}20{E} direction is in contrast with seismic sources identified from geodetic inversions, which favour but not exclusively the {N}110-120{E} rupture directions, suggesting that the 1994 and 2004 events occurred on conjugate faults. {I}n any event, the recent seismicity is thus concentrated on sinistral {N}10-20{E} or {N}110-120{E} dextral strike-slip faults, which surface expressions remain hidden below the 3-5 km-thick {R}if nappes, as shown by the tomographic images build from the aftershock sequence and the concentration of the seismicity below 3 km. {T}hese observations may suggest that strain decoupling between the thrusted cover and the underlying bedrock and highlights the difficulty to determine the source properties of moderate events with blind faults even in the case of good quality recorded data.},
  keywords = {{A}l {H}oceima ; {S}eismicity ; {A}ftershocks sequence ; {F}ocal mechanisms ; {T}omography ; {T}eleseismic inversion ; {MAROC}},
  booktitle = {},
  journal = {{J}ournal of {G}eodynamics},
  volume = {77},
  numero = {},
  pages = {89--109},
  ISSN = {0264-3707},
  year = {2014},
  DOI = {10.1016/j.jog.2013.12.004},
  URL = {https://www.documentation.ird.fr/hor/fdi:010062241},
}