Felt earthquakes during 2012 in Peru

Peru is located in the South American subduction zone where the Nazca Plate subducts beneath the South American continent at a rate of 7 cm/yr in a NEE direction. This rapid subduction originates strong seismic coupling all along the subduction interface and gives raise to the continuous occurrence of earthquakes of light to moderate magnitude (M>4t<6) and less frequently to earthquakes of strong to large magnitude (M>7).

In Peru the Instituto Geofísico del Peru (IGP) is the official government dependency in charge of the earthquake monitoring and surveillance all along its territory. Regularly in Peru there are several earthquakes every day, but only those that are felt by the population are reported by IGP, those that are not felt are processed and stored in a database.

In 2012 the IGP reported the occurrence of 225 felt earthquakes. This number compared to previous years (in 2010=154, in 2011=138 ) caused some surprise because to its increment, nevertheless it is necessary to mention that during last year the IGP seismic network was improved through the installation of new stations and also the communication technology (social networks) and reports from the people improved. However I cannot discard that the seismicity rate has increased during 2012  specially in Lima where I do live since some years ago and where this past year personally I felt several earthquakes, more than the normal average.

The 225 felt earthquakes reported by IGP show magnitudes ranging between 3.5 and 6.4 with depths varying between 10km and 169km. From this list the largest one occurred on August 2nd 2012 at 04:38 GMT with a magnitude of 6.4 ML (lat. -74.19, lon -8.64), the hypocenter was located at 150 of depth registering intensities of IV-V in Pucallpa, IV in Huanuco III in Trujillo and II in Lima. Fortunately any of this events caused casualties. Here is the list with the 10 most large earthquake occurred in Peru during 2012:

02/08/2012	4:38	-8.64	-74.19	150	6.4	IV-V Pucallpa; III-IV Huanuco; III Trujillo; II Lima
30/01/2012	0:10	-14.37	-76.02	54	6.3	V Ica; IV-V Pisco; IV Chincha, Palpa, San Vicente de Cañete
14/05/2012	5:00	-18.05	-70.06	98	6.1	IV Tacna; III-IV Ilo, Moquegua; III Arequipa; II-III Ocoña
07/06/2012	11:03	-15.98	-72.75	110	6.1	V Chuquibamba; IV Caraveli; III-IV Arequipa
10/11/2012	9:57	-8.88	-75.19	135	6.0	IV-V Aguaytia
27/11/2012	22:09	-4.68	-76.26	143	5.8	III Yurimaguas, Lagunas; II-III Moyobamba
02/07/2012	23:31	-14.71	-76.13	34	5.6	IV Ica
06/05/2012	7:40	-13.93	-75.96	65	5.5	V Pisco; III-IV Ica; II-III Lima
25/10/2012	15:49	-5.83	-76.43	110	5.5	III-IV Yurimaguas; III Moyobamba; II Lamas
26/02/2012	3:08	-18.82	-69.63	117	5.4	II Tacna, Tarata
07/08/2012	5:30	-13.50	-77	46	5.4	II-III San Vicente de Cañete; II Ica, Lima

The Figure shows the spatial distribution of the 225 felt earthquakes occurred in Peru during 2012. The size of the circle is proportional to the magnitude of the earthquake (4, 5, 6 and 7 ML) and the color is referred to the depth according to the colorbar. We observe that the seismicity is mostly concentrated offshore in central Peru in front of the Ica and Lima provinces, this fact supports my guess about the increment of the seismicity around Lima. In general all along Peru we observe that shallow seismicity (0-60km) is mostly concentrated between the trench and the coastline and it is directly related to the friction process of the Nazca and South American plates. Inland the shallow seismicity decreases in number, the few events most probably are related to the active quaternary faulting. Moreover, we also observe more intermediate events inland, some clusters are clearly distinguished at -77W, -5S and -75W, -9S with both probably related to the internal deformation of the subducting slab. Some moderate intermediate events occurred also in Arequipa and Tacna. In Northern Peru the seismicity rate during 2012 in minor.