  Sunspot regions often form complexes of activity that may live for several
solar rotations, and represent a major component of the Sun's magnetic
activity. It had been suggested that the close appearance of active regions in
space and time might be related to common subsurface roots, or "nests" of
activity. EUV images show that the active regions are magnetically connected in
the corona, but subsurface connections have not been established. We
investigate the subsurface structure and dynamics of a large complex of
activity, NOAA 10987-10989, observed during the SOHO/MDI Dynamics run in
March-April 2008, which was a part of the Whole Heliospheric Interval (WHI)
campaign. The active regions in this complex appeared in a narrow latitudinal
range, probably representing a subsurface toroidal flux tube. We use the MDI
full-disk Dopplergrams to measure perturbations of travel times of acoustic
waves traveling to various depths by using time-distance helioseismology, and
obtain sound-speed and flow maps by inversion of the travel times. The
subsurface flow maps show an interesting dynamics of decaying active regions
with persistent shearing flows, which may be important for driving the flaring
and CME activity, observed during the WHI campaign. Our analysis, including the
seismic sound-speed inversion results and the distribution of deep-focus
travel-time anomalies, gave indications of diverging roots of the magnetic
structures, as could be expected from $\Omega$-loop structures. However, no
clear connection in the depth range of 0-48 Mm among the three active regions
in this complex of activity was detected.
