Supplementary Material

Fig. S1. Gravity stations disposed over the study area used to obtain the Bouguer anomaly map in Fig. 4B. The red polygon indicates the area covered by the aerogravity survey of the Projeto Bacia do Parnaíba realized on 2006, covering a 950 km x 980 km area. In blue it is indicated the area covered by the 2’x2’ grid of Bouguer gravity anomaly.

Fig. S2. Radially Averaged Power Spectrum of the Bouguer gravity anomaly of Fig. 4B, used to obtain the three groups of anomalies in Fig. 5. The groups of sources are identified with the red lines according to the method of Spector and Grant (1970).

Fig. S3. Local field due only to topography, calculated at a depth of 10 km, showing relatively lower stress magnitudes. Note that the stress scale in the legend of this figure was reduced for visualization. Blue arrows denote SHmax approximation and red arrows SHmin. Note that the calculated stresses are deviatoric.

Fig. S4. Total stress field model 3, assuming a regional E-W compression of 10 MPa, calculated at a depth of 10 km. Blue arrows denote SHmax approximation and red arrows SHmin. Note that the calculated stresses are deviatoric.

Fig. S5. Total stress field model 6, assuming a regional E-W compression of 25 MPa, calculated at a depth of 10 km. Blue arrows denote SHmax approximation and red arrows SHmin. Note that the calculated stresses are deviatoric.

Fig. S6. Total stress field model 7, assuming a regional E-W compression of 30 MPa, calculated at a depth of 10 km. Blue arrows denote SHmax approximation and red arrows SHmin. Note that the calculated stresses are deviatoric.

Table S1. Earthquake focal mechanisms used in Fig. 2B.

Province

Locality

Year

Reference

Style

Quality

Parnaíba

Maranhão (MA)

2017

(Dias et al., 2018)

SS

C1

Borborema

Senador Sá – CE

1997-1998

(França et al., 2004)

SS

C2

Hidrolândia – CE

1991

(Ferreira et al., 1998)

TF

C2

Groaíras – CE

1988

(Ferreira et al., 1998)

SS

C2

Sobral – CE

2008

(Oliveira et al., 2010)

SS

C2

Irauçuba – CE

1991

(Ferreira et al., 1998)

TF, NF

C2, C2

2015 – 2016

(Menezes, 2017)

NF

C1

Santana do Acaraú – CE

2010

(Oliveira et al., 2015)

SS

C2

Castanhão – CE

2010

(Castro Nunes et al., 2011)

TF

C2

Cascavel – CE

1980

(Assumpção et al., 1985)

SS

C2

1993-1994

(Ferreira et al., 1998)

SS

C2

1997-1998

(Vilar, 2000)

SS, SS

D, D

Palhano – CE

1989

(Ferreira et al., 1998)

SS

C2

Tabuleiro Grande – RN

1993

(Ferreira et al., 1998)

TF

C2

Augusto Severo – RN

1990 – 1991

(Ferreira et al., 1998)

TF

D

Açu Reservoir – RN

1989

(Ferreira et al., 1995)

SS

D

1990-1991

(Ferreira et al., 1995)

SS, SS

C2, C2

1989-1991

(Ferreira et al., 1998)

SS

C2

1994 – 1997

(Do Nascimento et al., 2004)

SS

C2

2012-2013

(Ferreira et al., 2018)

SS

C1

Pedra Preta – RN

2011

(Dantas et al., 2011)

NF

C2

2013-2014

(Costa et al., 2017)

NF

C1

João Câmara – RN

1986-1987

(Ferreira et al., 1987)

SS

C1

1989

(Costa et al., 1989)

SS

C1

1986-1987

(Takeya, 1992)

SS, SS

C1, C1

Poço Branco – RN

1987-1988

(Takeya, 1992)

SS, SS

C2, C2

Taipu – RN

2009 – 2010

(Lima Neto et al., 2010)

NF

C2

Caruaru – PE

1991

(Ferreira et al., 1998)

NF

C2

2002

(Ferreira et al., 2008)

SS

C2

Belo Jardim – PE

2004

(Lopes et al., 2010)

NF

C2

São Caetano – PE

2010

(Lima Neto et al., 2013)

NF

C1

2016

(Coelho, 2019)

SS, SS, NF

C1, C2, C1

Santa Luzia – PE

2007

(Lima Neto et al., 2013)

NF

C2

Barra do Chata – PE

2010

(Lima Neto et al., 2014)

NF

C2

Serra Verde – PE

2010

(Lima Neto et al., 2014)

NF

C2

São Francisco

Baixa Grande – BA

2018

Unpublished Report of UFRN

SS

C2

Correntina – BA

2004

(Lopes, 2008)

TF

C2

Manga – MG

1990

(Assumpção et al., 1990)

TF

C2

Caraíbas-Itacarambi – MG

2007

(Chimpliganond et al., 2010)

TF

C1

Montes Claros – MG

2012-2013

(Agurto-Detzel et al., 2015)

TF

C1

Tocantins

Mara Rosa – GO

2010

(Barros et al., 2015)

TF

C1

Brasília – DF

2000

(Agurto-Detzel et al., 2015)

SS

C2

Mantiqueira

Encruzilhada – BA

1990

(Veloso, 1990)

TF

D

Note: The acronyms MA, CE, RN, PE, BA, MG, GO and DF refers to the Brazilian states of Maranhão, Ceará, Rio Grande do Norte, Pernambuco, Bahia, Minas Gerais, Goiás e Distrito Federal, respectively. Also, the faulting styles NF, SS and TF means normal fault, strike-slip and thrust fault. The quality rank scheme used here is the same of the present World Stress Map project adapted by Assumpção et al. (2016) for Brazil, which classifies focal mechanisms as C1, C2 or D, from the more to the less reliable to indicate the SHmax orientation. More details can be seen in Assumpção et al. (2016).

References

Agurto-Detzel, H., Assumpção, M., Ciardelli, C., Albuquerque, D.F., Barros, L. V., França, G.S.L., 2015. The 2012–2013 Montes Claros earthquake series in the São Francisco Craton, Brazil: new evidence for non-uniform intraplate stresses in mid-plate South America. Geophys. J. Int. 200, 216–226. https://doi.org/10.1093/gji/ggu333

Assumpção, M., Dias, F.L., Zevallos, I., Naliboff, J.B., 2016. Intraplate stress field in South America from earthquake focal mechanisms. J. South Am. Earth Sci. 71, 278–295. https://doi.org/10.1016/j.jsames.2016.07.005

Assumpção, M., Suarez, G., Veloso, J., 1985. Fault plane solutions of intraplate earthquakes in brazil: Some constraints on the regional stress field. Tectonophysics 113, 283–293. https://doi.org/10.1016/0040-1951(85)90201-X

Assumpção, M., Veloso, J.A.V., Barbosa, J.R., Blum, M.L.B., Carvalho, J.M., NEVES, E., Bassini, A., 1990. The Manga earthquakes, MG, March of 1990., in: XXXVI Brazilian Congress of Geology. Natal/RN, pp. 2154–2159. https://doi.org/10.1029/2002GC000464

Barros, L. V., Assumpção, M., Chimpliganond, C., Carvalho, J.M., Von Huelsen, M.G., Caixeta, D., França, G.S., de Albuquerque, D.F., Ferreira, V.M., Fontenele, D.P., 2015. The Mara Rosa 2010 GT-5 earthquake and its possible relationship with the continental-scale transbrasiliano lineament. J. South Am. Earth Sci. 60, 1–9. https://doi.org/10.1016/j.jsames.2015.02.002

Castro Nunes, B.I. de, do Nascimento, A.F., Ferreira, J., Assumpção, M., Menezes, E.A. de, 2011. Reservoir-Induced Seismicity at Castanhão (NE Brazil), in: 12th International Congress of the Brazilian Geophysical Society & EXPOGEF. Society of Exploration Geophysicists and Brazilian Geophysical Society, Rio de Janeiro, Brazil, pp. 1404–1407. https://doi.org/10.1190/sbgf2011-290

Chimpliganond, C., Assumpção, M., Von Huelsen, M., França, G.S., 2010. The intracratonic Caraíbas–Itacarambi earthquake of December 09, 2007 (4.9 mb), Minas Gerais State, Brazil. Tectonophysics 480, 48–56. https://doi.org/10.1016/j.tecto.2009.09.016

Coelho, S.A., 2019. Caracterização da atividade sísmica de 2016 no Lineamento Pernambuco, São Caetano, NE Brasil. Universidade Federal do Rio Grande do Norte.

Costa, C.D.S., Ferreira, J.M., Lima Neto, H.C. de, Bezerra, F.H.R., Sousa, M.O.L., 2017. Sismicidade intraplaca em Pedra Preta (RN) no período de 2013 a 2014. Geol. USP. Série Científica 17, 123–129. https://doi.org/10.11606/issn.2316-9095.v17-121972

Costa, J., Ferreira, J., Oliveira, R., Assumpção, M., 1989. O sismo de Joao Camara de 10 de Março de 1989 (mb=4.9), in: In 1st International Congress of the Brazilian Geophysical Society. pp. 371–375.

Dantas, R.R.S., Lima Neto, H.C., Ferreira, J.M., do Nascimento, A.F., Assumpção, M., Bezerra, F.H.R., Menezes, E.A.., Spinelli, R.M.R.P., Costa, N.P., 2011. Atividade sísmica em Pedra Preta-RN em 2010, in: 12th International Congress of the Brazilian Geophysical Society & EXPOGEF. Society of Exploration Geophysicists Unconventional Resources Technology Conference, Rio de Janeiro, Brazil. https://doi.org/https://doi.org/10.1190/sbgf2011-412

Dias, F.L., Assumpção, M., Bianchi, M.B., Barros, L. V., Carvalho, J.M., 2018. The intraplate Maranhão earthquake of 2017 January 3, northern Brazil: evidence for uniform regional stresses along the Brazilian equatorial margin. Geophys. J. Int. 213, 387–396. https://doi.org/10.1093/gji/ggx560

Do Nascimento, A.F., Cowie, P.A., Lunn, R.J., Pearce, R.G., 2004. Spatio-temporal evolution of induced seismicity at Açu reservoir, NE Brazil. Geophys. J. Int. 158, 1041–1052. https://doi.org/10.1111/j.1365-246X.2004.02351.x

Ferreira, J.M., Bezerra, F.H.R., Sousa, M.O.L., do Nascimento, A.F., Sá, J.M., França, G.S., 2008. The role of Precambrian mylonitic belts and present-day stress field in the coseismic reactivation of the Pernambuco lineament, Brazil. Tectonophysics 456, 111–126. https://doi.org/10.1016/j.tecto.2008.01.009

Ferreira, J.M., De Oliveira, R.T., Assumpcao, M., Moreira, J.A.M., Pearce, R.G., Takeya, M.K., 1995. Correlation of seismicity and water level in the Acu reservoir - an example from northeast Brazil. Bull. - Seismol. Soc. Am. 85, 1483–1489.

Ferreira, J.M., Oliveira, T., Takeya, M.K., Assumpção, M., 1998. Superposition of local and regional stresses in northeast Brazil: evidence from focal mechanisms around the Potiguar marginal basin. Geophys. J. Int. 134, 341–355. https://doi.org/10.1046/j.1365-246x.1998.00563.x

Ferreira, J.M., Takeya, M., Costa, J.M., Moreira, J.A., Assumpção, M., Veloso, J.A. V., Pearce, R.G., 1987. A continuing intraplate earthquake sequence near João Câmara, northeastern Brazil-Preliminary results. Geophys. Res. Lett. 14, 1042–1045. https://doi.org/10.1029/GL014i010p01042

Ferreira, P.A.R., Ferreira, J.M., do Nascimento, A.F., Bezerra, F.H.R., Lima Neto, H.C., Menezes, E.A.S., 2018. Seismicity Migration Induced by the Açu Reservoir, Northeast Brazil, and Implications for Fault Hydraulic Variability. Bull. Seismol. Soc. Am. 108, 3107–3118. https://doi.org/10.1785/0120170372

França, G.S., Ferreira, J.M., Takeya, M.K., 2004. Seismic activity in Senador Sá-CE, Brazil, 1997-1998. Rev. Bras. Geofísica 22. https://doi.org/10.1590/S0102-261X2004000200002

Lima Neto, H.C., Ferreira, J.M., Bezerra, F.H.R., Assumpção, M., do Nascimento, A.F., Sousa, M.O.L., Menezes, E.A.S., 2014. Earthquake sequences in the southern block of the Pernambuco Lineament, NE Brazil: Stress field and seismotectonic implications. Tectonophysics 633, 211–220. https://doi.org/10.1016/j.tecto.2014.07.010

Lima Neto, H.C., Ferreira, J.M., Bezerra, F.H.R., Assumpção, M.S., do Nascimento, A.F., Sousa, M.O.L., Menezes, E.A.S., 2013. Upper crustal earthquake swarms in São Caetano: Reactivation of the Pernambuco shear zone and trending branches in intraplate Brazil. Tectonophysics 608, 804–811. https://doi.org/10.1016/j.tecto.2013.08.001

Lima Neto, H.C., Ferreira, J.M., do Nascimento, A.F., Bezerra, F.H.R., Spineli, R.M.., Costa, N.P., Menezes, E.A.S., 2010. Estudo Das Réplicas Do Sismo De Magnitude 4.3 Em Taipu - Rn Ocorrido Em 2010, in: IV Simpósio Brasileiro de Geofísica. SBGF.

Lopes, A.E.V., 2008. Mecanismos focais e esforços litosféricos no brasil. Universidade de São Paulo.

Lopes, A.E. V., Assumpção, M., do Nascimento, A.F., Ferreira, J.M., Menezes, E.A.S., Barbosa, J.R., 2010. Intraplate earthquake swarm in Belo Jardim, NE Brazil: reactivation of a major Neoproterozoic shear zone (Pernambuco Lineament). Geophys. J. Int. 180, 1303–1312. https://doi.org/10.1111/j.1365-246X.2009.04485.x

Menezes, E.A.S., 2017. Estudo da atividade sísmica em Irauçuba – CE entre setembro de 2015 a março de 2016. Universidade Federal do Rio Grande do Norte.

Oliveira, P.H.S., Ferreira, J.M., Bezerra, F.H.R., Assumpção, M., do Nascimento, A.F., Sousa, M.O.L., Menezes, E.A.S., 2015. Influence of the continental margin on the stress field and seismicity in the intraplate Acaraú Seismic Zone, NE Brazil. Geophys. J. Int. 202, 1453–1462. https://doi.org/10.1093/gji/ggv211

Oliveira, P.H.S., Ferreira, J.M., do Nascimento, A.F., Bezerra, F.H.R., Soares, J.E., Fuck, R., 2010. Estudo Da Sismicidade Na Região De Sobral – CE, NE Do Brasil, Em 2008, in: IV Simpósio Brasileiro de Geofísica. SBGF.

Spector, A., Grant, F.S., 1970. Statistical models for interpreting aeromagnetic data. Geophysics 35, 293–302. https://doi.org/10.1190/1.1440092

Takeya, M.K., 1992. High Precision Studies of an Intraplate Earthquake Sequence in Northeast Brazil. University of Edinburgh.

Veloso, J., 1990. Atividade sísmica de Encruzilhada-BA, in: 36th Brazilian Congresso of Geology. Natal/RN.

Vilar, C. da S., 2000. Estudo da Atividade Sísmica em Cascavel - CE com estações sismográficas digitais. Universidade Federal do Rio Grande do Norte.