applied sciences Article  
Lichenometric Analysis Applied to Bedrock Fault Scraps: The  
Sencelles Fault and the 1851 CE Mallorca Earthquake (Balearic Islands, Spain)  
[PERSON] 1,*c, [PERSON] 2, [PERSON] 3c, [PERSON] 4c, [PERSON] 5c and [PERSON] 6  
Departamento Geologia, Escuela Politecnica Superior de Avila, Universidad de Salamanca, 05003 Avila, Spain  
Departamento Edafologia, Escuela Tecnica Superior de Ingenieros Agronos, Universidad Politecnica de Madrid, 2800 Madrid, Spain; elvira.roquero@upmps.  
Instituto Geologico y Minero de Espana (IGME-CSIC), 28003 Madrid, Spain; [EMAIL_ADDRESS]  
Departamento Geologia, Geografia y Medio Ambiente, Universidad de Alcala, 28871 Alcala de Henares, Spain; [EMAIL_ADDRESS]  
Departamento Ingenieria del Terreno, Facultad de Ciencias, Universidad de Salamanca, 37008 Salamanca, Spain  
Departamento Geologia, Facultad de Ciencias, Universidad de Salamanca, 37008 Salamanca, Spain  
Correspondence: [EMAIL_ADDRESS]  
**Featured Application: The paper displays the analysis of lichen colonization of rocky fault-scraps to perform geochronological analyses and evidence ancient to historical earthquakes. This applied research shows the high sensitivity of vertical/horizontal position, geographical orientation and lithological nature of lichen colonized rock surfaces for the obtention of reliable lichen growth rates (LGR) applicable to geochronology.**  
**Abstract: The Sencelles Fault constitutes the main extensional structure of Mallorca Island (Spain), holds a NE-SE orientation, and has been identified as the possible seismic source of the 1851 CE Palma earthquake (VII EMS.) The SE termination of the fault (Sta. Eugenia Segment) features a linear bedrock fault scarp of a maximum of 3.15 m height. The last 840 m of this rocky scarp display a significant horizontal banding, with up to five differentially weathered ribbons colonized by lichens. The Inchemometric analysis is based on the measurement of 155 specimens of _Aspicillin calacana_ (_Ac_) and _Aspicillin calacana_ (_Ar_) in tombounces and funery movements (with inscribed dates) from the nearby cemeteries of Sta. Maria del Cami, Sta. Eugenia and Sencelles, to obtain the local lichen growth rates (LGR), with the two last graveyards being directly located in the fault zone. Lichens were measured on variously oriented (N, S, NE, SW, etc... ) horizontal and vertical surfaces, generating differentially oriented lichen populations (DOLPs) to be compared with the _Ac_ and _Ar_ specimens colonizing the studied fault scarp (38 measured individual specimens). After successive trial and error regression tests, vertical DOLPs resulted in the best appropriate groups for the analysis, with LGR of 0.23-0.31 mm/yr. Horizontal ones reached widths of up to 20 cm, with LGR up to 0.84 mm/yr, which were clearly oversized. The application of the selected LGR points to a human-induced origin for the thin basal lichen ribbon of the scarp (10-13 cm), which should have developed during the middle 20 th century (c. 1950-1966) because of documented ground leveling works. However, the second ribbon of the scarp (23-47 cm) shows exposure dates of 1852 \(\pm\) 40 (_Ar_) and 1841 \(\pm\) 59 (_Ac_), overlapping the date of the 1851 CE earthquake. The study is complemented with data from a fault trench excavated in the year 2002 at the toe of the scarp. The combined data of lichenometry, fault trenching, and the length of the analyzed fault scarp (c. 840 m) indicate that the studied segment of the fault cannot be considered a co-seismic surface faulting related to the 1851 CE event as a whole, but a relevant secondary earthquake effect on a pre-existing fault scarp (e.g., sympathetic ground ruptures).  
**Keywords:** sencelles fault; lichenometry; lichen growth rates; bedrock fault scarp; 1851 CE Palma earthquake; Mallorca Island; Spain