Environ Monit Assess (2012) 184:161–170 DOI 10.1007/s10661-011-1955-4 Determining the depositional pattern by resistivity–seismic inversion for the aquifer system of Maira area, Pakistan Gulraiz Akhter · Asim Farid · Zulfiqar Ahmad Received: 20 January 2010 / Accepted: 9 February 2011 / Published online: 8 March 2011 © Springer Science+Business Media B.V. 2011 Abstract Velocity and density measured in a well are crucial for synthetic seismic generation which is, in turn, a key to interpreting real seismic am- plitude in terms of lithology, porosity and fluid content. Investigations made in the water wells usually consist of spontaneous potential, resistiv- ity long and short normal, point resistivity and gamma ray logs. The sonic logs are not avail- able because these are usually run in the wells drilled for hydrocarbons. To generate the syn- thetic seismograms, sonic and density logs are required, which are useful to precisely mark the lithology contacts and formation tops. An attempt has been made to interpret the subsurface soil of the aquifer system by means of resistivity to seismic inversion. For this purpose, resistivity logs and surface resistivity sounding were used and the resistivity logs were converted to sonic logs whereas surface resistivity sounding data trans- formed into seismic curves. The converted sonic logs and the surface seismic curves were then used G. Akhter (B ) · A. Farid · Z. Ahmad Department of Earth Sciences, Quaid-i-Azam University, Islamabad, 45320, Pakistan e-mail: agulraiz@qau.edu.pk A. Farid e-mail: asam.farid@gmail.com Z. Ahmad e-mail: fz97@hotmail.com to generate synthetic seismograms. With the uti- lization of these synthetic seismograms, pseudo- seismic sections have been developed. Subsurface lithologies encountered in wells exhibit different velocities and densities. The reflection patterns were marked by using amplitude standout, charac- ter and coherence. These pseudo-seismic sections were later tied to well synthetics and lithologs. In this way, a lithology section was created for the alluvial fill. The cross-section suggested that the eastern portion of the studied area mainly consisted of sandy fill and the western portion constituted clayey part. This can be attributed to the depositional environment by the Indus and the Kabul Rivers. Keywords Resistivity · Seismic inversion · Aquifer · Deposition · Lithology · Sonic logs Introduction Maira area is in the southern part of Mardan Plain and is bounded by the latitude 33 ◦ 56 ′ to 34 ◦ 14 ′ N and longitude 72 ◦ 0 ′ to 72 ◦ 28 ′ E. The average altitude of the area is 350 m AMSL and the highest point is the center of the area with an altitude of 404 m. The alluvial plain covers the area of 379 km 2 . Maira branch canal lies in the north, while Badri Khwar nullah in the east, Kalpani nullah in the west and the Indus and the Kabul