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We have surveyed 401 color selected IRAS sources in the Galactic disk in theSiO J=1--0 v= 1 and 2 maser lines at 43 GHz, resulting in 254 (239 new)detections. The observed sources lie mostly in a strip of the inner Galacticdisk with boundaries -10<l<40 deg and |b|<3 deg. This survey provides radialvelocities of inner-disk stars for which optical measurements cannot be madedue to interstellar extinction. The SiO $l$--$v$ diagram in the area $-10<l<40deg exhibits fewer objects coincident with the molecular ring feature than theOH 1612 MHz source $l$--$v$ map does, indicating a slight difference of stellartype between SiO and OH emitting stars. After identifying all of the SiOdetected sources in the 2MASS near-infrared catalog, we computed theirluminosity distances based on the infrared fluxes. We then mapped these objectsonto the first quadrant of the Galactic plane. Combining the distances with theSiO radial-velocities, we obtained a pattern speed for SiO maser sources,Omega_P=21 (+- 13) km s^{-1} kpc^{-1}, between the distances 1 and 5.5 kpc,without the use of any dynamical models. The increase of the pattern speedtoward the Galactic center (up to 60 km s^{-1} kpc^{-1} between the distances,5.5 and 7 kpc) suggests the presence of two pattern speeds in the Galaxy.

SiO Maser Survey of IRAS Sources in the Inner Galactic Disk