Surface deformation of Long Valley caldera and Mono Basin, California, investigated with the SBAS-InSAR approach P. Tizzani a , P. Berardino a , F. Casu a,b , P. Euillades c,d , M. Manzo a,e , G.P. Ricciardi f , G. Zeni a,e , R. Lanari a, ⁎ a Istituto per il Rilevamento Elettromagnetico dell'Ambiente, National Research Council, Via Diocleziano 328, I-80124 Napoli, Italy b Dipartimento di Ingegneria Elettrica ed Elettronica, Università degli studi di Cagliari, Piazza d'Armi, I-09123 Cagliari, Italy c Conicet, Instituto CEDIAC, Facultad de Ingenierìa, Universidad Nac de Cuyo, Mendoza, Argentina d Temporarily at Istituto per il Rilevamento Elettromagnetico dell'Ambiente, National Research Council, Via Diocleziano 328, I-80124 Napoli, Italy e Dipartimento di Ingegneria e Fisica dell'Ambiente, Università degli Studi della Basilicata, Viale dell'Ateneo Lucano 10, I-85100 Potenza, Italy f Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Via Diocleziano 328, I-80124 Napoli, Italy Received 15 September 2006; received in revised form 13 November 2006; accepted 15 November 2006 Abstract We investigate the surface deformation of the eastern California area that includes Long Valley caldera and Mono Basin. We apply the SAR Interferometry (InSAR) algorithm referred to as Small BAseline Subset (SBAS) approach that allows us to generate mean deformation velocity maps and displacement time series for the investigated area. The results presented in this work represent an advancement of previous InSAR studies of the area that are mostly focused on the deformation affecting the caldera. In particular, the proposed analysis is based on 21 SAR data acquired by the ERS-1/2 sensors during the 1992–2000 time interval, and demonstrates the capability of the SBAS procedure to identify and analyze displacement patterns at different spatial scales for the overall area spanning approximately 5000 km 2 . Two previously unreported localized deformation effects have been detected at Paoha Island, located within the Mono Lake, and in the McGee Creek area within the Sierra Nevada mountains, a zone to the south of the Long Valley caldera. In addition a spatially extended uplift effect, which strongly affects the caldera, has been identified and analyzed in detail. The InSAR results clearly show that the displacement phenomena affecting the Long Valley caldera have a maximum in correspondence of the resurgent dome and are characterized by the sequence of three different effects: a 1992–1997 uplift background, a 1997–1998 unrest phenomenon and a 1998–2000 subsidence phase. Moreover, the analysis of the retrieved displacement time series allows us to map the extent of the zone with a temporal deformation behavior highly correlated with the detected three-phases deformation pattern: background uplift-unrest-subsidence. We show that the mapped area clearly extends outside the northern part of the caldera slopes; accordingly, we suggest that future inversion models take this new evidence into account. The final discussion is dedicated to a comparison between the retrieved InSAR measurements and a set of GPS and leveling data, confirming the validity of the results achieved through the SBAS- InSAR analysis. © 2006 Elsevier Inc. All rights reserved. Keywords: Differential SAR Interferometry; SBAS-InSAR; Microwave remote sensing; Long Valley caldera; Mono Basin; Caldera unrest 1. Introduction The Long Valley caldera and Mono Basin are located in eastern California, in an area surrounded to the west by the Sierra Nevada and to the east by the White Mountains. The Long Valley caldera, an east–west elongate oval depression with an extent of approximately 17 km by 32 km, was formed about 0.76 Ma B.P. (Hill & Prejean, 2005). Subsequently, between 0.76 and 0.6 Ma B.P., the caldera uplift and the rhyolitic lava flows eruption, referred to as early rhyolite, formed the resurgent dome (Bailey, 1989; Hill & Prejean, 2005). The Mono Basin consists of several landforms belonging to different volcanic centers such as the Mono and Inyo chains, the Paoha and Negit Islands and some others (see Bursik & Sieh, 1989) with the centers of the basin being formed within the last 40,000 years. Remote Sensing of Environment 108 (2007) 277 – 289 www.elsevier.com/locate/rse ⁎ Corresponding author. Tel.: +39 0815707999; fax: +39 0815705734. E-mail address: lanari.r@irea.cnr.it (R. Lanari). 0034-4257/$ - see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.rse.2006.11.015